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Alcohol intoxication

Alcohol intoxication, also known in overdose as alcohol poisoning, commonly described as drunkenness or inebriation, is the behavior and physical effects caused by a recent consumption of alcohol. In addition to the toxicity of ethanol, the main psychoactive component of alcoholic beverages, other physiological symptoms may arise from the activity of acetaldehyde, a metabolite of alcohol. These effects may not arise until hours after ingestion and may contribute to the condition colloquially known as a hangover. The term intoxication is commonly used when large amount of alcohol is consumed along with physical symptoms and deleterious health effects.

Symptoms of intoxication at lower doses may include mild sedation and poor coordination. At higher doses, there may be slurred speech, trouble walking, and vomiting. Extreme doses may result in a respiratory depression, coma, or death. Complications may include seizures, aspiration pneumonia, low blood sugar, and injuries or self-harm such as suicide. Alcohol intoxication can lead to alcohol-related crime with perpetrators more likely to be intoxicated than victims.

Alcohol intoxication typically begins after two or more alcoholic drinks. Alcohol has the potential for abuse. Risk factors include a social situation where heavy drinking is common and a person having an impulsive personality. Diagnosis is usually based on the history of events and physical examination. Verification of events by witnesses may be useful. Legally, alcohol intoxication is often defined as a blood alcohol concentration (BAC) of greater than 5.4–17.4 mmol/L (25–80 mg/dL or 0.025–0.080%). This can be measured by blood or breath testing. Alcohol is broken down in the human body at a rate of about 3.3 mmol/L (15 mg/dL) per hour, depending on an individual's metabolic rate (metabolism). The DSM-5 defines alcohol intoxication as at least one of the following symptoms that developed during or close after alcohol ingestion: slurred speech, incoordination, unsteady walking/movement, nystagmus (uncontrolled eye movement), attention or memory impairment, or near unconsciousness or coma.

Management of alcohol intoxication involves supportive care. Typically this includes putting the person in the recovery position, keeping the person warm, and making sure breathing is sufficient. Gastric lavage and activated charcoal have not been found to be useful. Repeated assessments may be required to rule out other potential causes of a person's symptoms.

Acute intoxication has been documented throughout history, and alcohol remains one of the world's most widespread recreational drugs. Some religions consider alcohol intoxication to be a sin.

Symptoms
Alcohol intoxication leads to negative health effects due to the recent drinking of large amount of ethanol (alcohol). When severe it may become a medical emergency. Some effects of alcohol intoxication, such as euphoria and lowered social inhibition, are central to alcohol's desirability.

As drinking increases, people become sleepy or fall into a stupor. At very high blood alcohol concentrations, for example above 0.3%, the respiratory system becomes depressed and the person may stop breathing. Comatose patients may aspirate their vomit (resulting in vomitus in the lungs, which may cause "drowning" and later pneumonia if survived). CNS depression and impaired motor coordination along with poor judgment increase the likelihood of accidental injury occurring. It is estimated that about one-third of alcohol-related deaths are due to accidents and another 14% are from intentional injury.

In addition to respiratory failure and accidents caused by its effects on the central nervous system, alcohol causes significant metabolic derangements. Hypoglycaemia occurs due to ethanol's inhibition of gluconeogenesis, especially in children, and may cause lactic acidosis, ketoacidosis, and acute kidney injury. Metabolic acidosis is compounded by respiratory failure. Patients may also present with hypothermia.

Pathophysiology

Alcohol is metabolized by a normal liver at the rate of about 8 grams of pure ethanol per hour. 8 grams or 10 mL is one British standard unit. An "abnormal" liver with conditions such as hepatitis, cirrhosis, gall bladder disease, and cancer is likely to result in a slower rate of metabolism.

Diagnosis
Alcohol intoxication is described as a mental and behavioural disorder by the International Classification of Diseases. (ICD-10). Drs; Definitive diagnosis relies on a blood test for alcohol, usually performed as part of a toxicology screen. Law enforcement officers in the United States and other countries often use breathalyzer units and field sobriety tests as more convenient and rapid alternatives to blood tests. There are also various models of breathalyzer units that are available for consumer use. Because these may have varying reliability and may produce different results than the tests used for law-enforcement purposes, the results from such devices should be conservatively interpreted.

Many informal intoxication tests exist, which, in general, are unreliable and not recommended as deterrents to excessive intoxication or as indicators of the safety of activities such as motor vehicle driving, heavy equipment operation, machine tool use, etc.

For determining whether someone is intoxicated by alcohol by some means other than a blood-alcohol test, it is necessary to rule out other conditions such as hypoglycemia, stroke, usage of other intoxicants, mental health issues, and so on. It is best if their behavior has been observed while the subject is sober to establish a baseline. Several well-known criteria can be used to establish a probable diagnosis. For a physician in the acute-treatment setting, acute alcohol intoxication can mimic other acute neurological disorders or is frequently combined with other recreational drugs that complicate diagnosis and treatment.

Management
Acute alcohol poisoning is a medical emergency due to the risk of death from respiratory depression or aspiration of vomit if vomiting occurs while the person is unresponsive. Emergency treatment strives to stabilize and maintain an open airway and sufficient breathing while waiting for the alcohol to metabolize. This can be done by removal of any vomit or, if the person is unconscious or has impaired gag reflex, intubation of the trachea.

Other measures may include Additional medication may be indicated for treatment of nausea, tremor, and anxiety.
 * Administer the vitamin thiamine to prevent Wernicke–Korsakoff syndrome, which can cause a seizure (more usually a treatment for chronic alcoholism, but in the acute context usually co-administered to ensure maximal benefit).
 * Hemodialysis if the blood concentration is very high at >130 mmol/L (>600 mg/dL)
 * Provide oxygen therapy as needed via nasal cannula or non-rebreather mask.
 * Administration of intravenous fluids in cases involving hypoglycemia and electrolyte imbalance.
 * While the medication metadoxine may speed the breakdown of alcohol, use in alcohol intoxication requires further study as of 2017. It is approved in a number of countries in Europe, as well as India and Brazil.

Hospital admissions
Alcohol intoxication was found to be prevalent in clinical populations within the United States involving people treated for trauma and in the age group of people aged within their 18th - 24th years (in a study of a group for the years 1999 - 2004). In the United States during the years 2010 - 2012, acute intoxication was found to be the direct cause of an average of 2,221 deaths, in the sample group of those aged within their 15th year or older. The same mortality route is thought to cause indirectly more than 30,000 deaths per year.

Prognosis

A normal liver detoxifies the blood of alcohol over a period of time that depends on the initial level and the patient's overall physical condition. An abnormal liver will take longer but still succeeds, provided the alcohol does not cause liver failure.

People having drunk heavily for several days or weeks may have withdrawal symptoms after the acute intoxication has subsided.

A person consuming a dangerous amount of alcohol persistently can develop memory blackouts and idiosyncratic intoxication or pathological drunkenness symptoms. Long-term persistent consumption of excessive amounts of alcohol can cause liver damage and have other deleterious health effects.

Society and culture

Alcohol intoxication is a risk factor in some cases of catastrophic injury, in particular for unsupervised recreational activity. A study in the province of Ontario based on epidemiological data from 1986, 1989, 1992, and 1995 states that 79.2% of the 2,154 catastrophic injuries recorded for the study were preventable, of which 346 (17%) involved alcohol consumption. The activities most commonly associated with alcohol-related catastrophic injury were snowmobiling (124), fishing (41), diving (40), boating (31) and canoeing (7), swimming (31), riding an all-terrain vehicle (24), and cycling (23). These events are often associated with unsupervised young males, often inexperienced in the activity, and may result in drowning. Alcohol use is also associated with unsafe sex.

Legal issues

Laws on drunkenness vary. In the United States, it is a criminal offense for a person to be drunk while driving a motorized vehicle, except in Wisconsin, where it is only a fine for the first offense. It is also a criminal offense to fly an aircraft or (in some American states) to assemble or operate an amusement park ride while drunk. Similar laws also exist in the United Kingdom and most other countries.

In some countries, it is also an offense to serve alcohol to an already-intoxicated person, and, often, alcohol can only be sold by persons qualified to serve responsibly through alcohol server training.

The blood alcohol content (BAC) for legal operation of a vehicle is typically measured as a percentage of a unit volume of blood. This percentage ranges from 0.00% in Romania and the United Arab Emirates; to 0.05% in Australia, South Africa, Germany, Scotland, and New Zealand (0.00% for underage individuals); to 0.08% in England and Wales, the United States and Canada.

The United States Federal Aviation Administration prohibits crew members from performing their duties within eight hours of consuming an alcoholic beverage, while under the influence of alcohol, or with a BAC greater than 0.04%.

In the United States, the United Kingdom, and Australia, public intoxication is a crime (also known as "being drunk and disorderly" or "being drunk and incapable").

In some countries, there are special facilities, sometimes known as "drunk tanks", for the temporary detention of persons found to be drunk.

Christianity
Some religious groups permit the consumption of alcohol; some permit consumption but prohibit intoxication; others prohibit any amount of alcohol consumption altogether. Many denominations of Christianity, such as Catholicism, Orthodoxy and Lutheranism, use wine as a part of the Eucharist and permit its consumption, but consider it sinful to become intoxicated.

Romans 13:13–14, 1 Corinthians 6:9–11, Galatians 5:19–21 and Ephesians 5:18 are among a number of other Bible passages that speak against intoxication.

While some Protestant Christian denominations prohibit the consumption of alcohol based upon biblical passages that condemn drunkenness, but others allow a moderate rate of consumption.

In the Church of Jesus Christ of Latter-day Saints, alcohol consumption is forbidden, and teetotalism has become a distinguishing feature of its members. Jehovah's Witnesses allow moderate alcohol consumption among its members.

Islam
In the Quran,  there is a prohibition on the consumption of grape-based alcoholic beverages, and intoxication is considered an abomination in the hadith of Muhammad. The schools of thought of Islamic jurisprudence have interpreted this as a strict prohibition of the consumption of all types of alcohol and declared it to be haram (lit. 'forbidden [in Islam]'), although other uses may be permitted.

Buddhism
In Buddhism, in general, the consumption of intoxicants is discouraged for both monastics and lay followers. Many Buddhists observe a basic code of ethics known as the five precepts, of which the fifth precept is an undertaking to refrain from the consumption of intoxicating substances (except for medical reasons). In the bodhisattva vows of the Brahmajala Sutra, observed by Mahayana Buddhist communities, distribution of intoxicants is likewise discouraged, as well as consumption.

Hinduism
In the Gaudiya Vaishnavism branch of Hinduism, one of the four regulative principles forbids the taking of intoxicants, including alcohol.

Judaism

In the Bible, the Book of Proverbs contains several chapters related to the negative effects of drunkenness and warns to stay away from intoxicating beverages. The Book of Genesis refers to the use of wine by Lot's daughters to rape him. The story of Samson in the Book of Judges tells of a monk from the Israelite tribe of Dan who, as a Nazirite, is prohibited from cutting his hair and drinking wine. Proverbs 31:4 warns against kings and other rulers drinking wine and similar alcoholic beverages, Proverbs 31:6–7 promotes giving such beverages to the perishing and wine to those whose lives are bitter as a coping mechanism against the likes of poverty and other troubles.

In Judaism, in accordance with the biblical stance against drinking, drinking wine is restricted for priests. The biblical command to sanctify the Sabbath and other holidays has been interpreted as having three ceremonial meals with wine or grape juice, known as Kiddush. A number of Jewish marriage ceremonies end with the bride and groom drinking a shared cup of wine after reciting seven blessings; this occurs after a fasting day in some Ashkenazi traditions. It has been customary and in many cases even mandated to drink moderately so as to stay sober, and only after the prayers are over.

During the Seder on Passover, there is an obligation to drink four ceremonial cups of wine while reciting the Haggadah. It has been assumed as the source of the wine-drinking ritual at communion in some Christian groups. During Purim, there is an obligation to become intoxicated; however, as with many other decrees, this has been avoided in many communities by allowing sleep during the day as a replacement.

During the U.S. Prohibition era in the 1920s, a rabbi from the Reform Judaism movement proposed using grape juice for the ritual instead of wine. Although refuted at first, the practice became widely accepted by orthodox Jews as well.

Other animals
In the film Animals Are Beautiful People, an entire section was dedicated to showing many different animals including monkeys, elephants, hogs, giraffes, and ostriches, eating over-ripe marula tree fruit causing them to sway and lose their footing in a manner similar to human drunkenness. Birds may become intoxicated with fermented berries and some die colliding with hard objects when flying under the influence.

In elephant warfare, practiced by the Greeks during the Maccabean revolt and by Hannibal during the Punic wars, it has been recorded that the elephants would be given wine before the attack, and only then would they charge forward after being agitated by their driver.

It is a regular practice to give small amounts of beer to race horses in Ireland. Ruminant farm animals have natural fermentation occurring in their stomach, and adding alcoholic beverages in small amounts to their drink will generally do them no harm, and will not cause them to become drunk.

Alcoholic beverages are extremely harmful to dogs, and often for reasons of additives such as xylitol, an artificial sweetener in some mixers. Dogs can absorb ethyl alcohol in dangerous amounts through their skin as well as through drinking the liquid or consuming it in foods. Even fermenting bread dough can be dangerous to dogs. In 1999, one of the royal footmen for Britain's Queen Elizabeth II was demoted from Buckingham Palace due to his "party trick" of spiking the meals and drinks of the Queen's pet corgi dogs with alcohol which in turn would lead the dogs to run around drunk.

title: Alcohol intoxication


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Data compression

In information theory, data compression, source coding, or bit-rate reduction is the process of encoding information using fewer bits than the original representation. Any particular compression is either lossy or lossless. Lossless compression reduces bits by identifying and eliminating statistical redundancy. No information is lost in lossless compression. Lossy compression reduces bits by removing unnecessary or less important information. Typically, a device that performs data compression is referred to as an encoder, and one that performs the reversal of the process (decompression) as a decoder.

The process of reducing the size of a data file is often referred to as data compression. In the context of data transmission, it is called source coding: encoding is done at the source of the data before it is stored or transmitted. Source coding should not be confused with channel coding, for error detection and correction or line coding, the means for mapping data onto a signal.

Compression is useful because it reduces the resources required to store and transmit data. Computational resources are consumed in the compression and decompression processes. Data compression is subject to a space-time complexity trade-off. For instance, a compression scheme for video may require expensive hardware for the video to be decompressed fast enough to be viewed as it is being decompressed, and the option to decompress the video in full before watching it may be inconvenient or require additional storage. The design of data compression schemes involves trade-offs among various factors, including the degree of compression, the amount of distortion introduced (when using lossy data compression), and the computational resources required to compress and decompress the data.

Lossless
Lossless data compression algorithms usually exploit statistical redundancy to represent data without losing any information, so that the process is reversible. Lossless compression is possible because most real-world data exhibits statistical redundancy. For example, an image may have areas of color that do not change over several pixels; instead of coding "red pixel, red pixel, ..." the data may be encoded as "279 red pixels". This is a basic example of run-length encoding; there are many schemes to reduce file size by eliminating redundancy.

The Lempel–Ziv (LZ) compression methods are among the most popular algorithms for lossless storage. DEFLATE is a variation on LZ optimized for decompression speed and compression ratio, but compression can be slow. In the mid-1980s, following work by Terry Welch, the Lempel–Ziv–Welch (LZW) algorithm rapidly became the method of choice for most general-purpose compression systems. LZW is used in GIF images, programs such as PKZIP, and hardware devices such as modems. LZ methods use a table-based compression model where table entries are substituted for repeated strings of data. For most LZ methods, this table is generated dynamically from earlier data in the input. The table itself is often Huffman encoded. Grammar-based codes like this can compress highly repetitive input extremely effectively, for instance, a biological data collection of the same or closely related species, a huge versioned document collection, internet archival, etc. The basic task of grammar-based codes is constructing a context-free grammar deriving a single string. Other practical grammar compression algorithms include Sequitur and Re-Pair.

The strongest modern lossless compressors use probabilistic models, such as prediction by partial matching. The Burrows–Wheeler transform can also be viewed as an indirect form of statistical modelling. In a further refinement of the direct use of probabilistic modelling, statistical estimates can be coupled to an algorithm called arithmetic coding. Arithmetic coding is a more modern coding technique that uses the mathematical calculations of a finite-state machine to produce a string of encoded bits from a series of input data symbols. It can achieve superior compression compared to other techniques such as the better-known Huffman algorithm. It uses an internal memory state to avoid the need to perform a one-to-one mapping of individual input symbols to distinct representations that use an integer number of bits, and it clears out the internal memory only after encoding the entire string of data symbols. Arithmetic coding applies especially well to adaptive data compression tasks where the statistics vary and are context-dependent, as it can be easily coupled with an adaptive model of the probability distribution of the input data. An early example of the use of arithmetic coding was in an optional (but not widely used) feature of the JPEG image coding standard. It has since been applied in various other designs including H.263, H.264/MPEG-4 AVC and HEVC for video coding.

Archive software typically has the ability to adjust the "dictionary size", where a larger size demands more random-access memory during compression and decompression, but compresses stronger, especially on repeating patterns in files' content.

Lossy
In the late 1980s, digital images became more common, and standards for lossless image compression emerged. In the early 1990s, lossy compression methods began to be widely used. In these schemes, some loss of information is accepted as dropping nonessential detail can save storage space. There is a corresponding trade-off between preserving information and reducing size. Lossy data compression schemes are designed by research on how people perceive the data in question. For example, the human eye is more sensitive to subtle variations in luminance than it is to the variations in color. JPEG image compression works in part by rounding off nonessential bits of information. A number of popular compression formats exploit these perceptual differences, including psychoacoustics for sound, and psychovisuals for images and video.

Most forms of lossy compression are based on transform coding, especially the discrete cosine transform (DCT). It was first proposed in 1972 by Nasir Ahmed, who then developed a working algorithm with T. Natarajan and K. R. Rao in 1973, before introducing it in January 1974. DCT is the most widely used lossy compression method, and is used in multimedia formats for images (such as JPEG and HEIF), video (such as MPEG, AVC and HEVC) and audio (such as MP3, AAC and Vorbis).

Lossy image compression is used in digital cameras, to increase storage capacities. Similarly, DVDs, Blu-ray and streaming video use lossy video coding formats. Lossy compression is extensively used in video.

In lossy audio compression, methods of psychoacoustics are used to remove non-audible (or less audible) components of the audio signal. Compression of human speech is often performed with even more specialized techniques; speech coding is distinguished as a separate discipline from general-purpose audio compression. Speech coding is used in internet telephony, for example, audio compression is used for CD ripping and is decoded by the audio players.

Lossy compression can cause generation loss.

Theory
The theoretical basis for compression is provided by information theory and, more specifically, Shannon's source coding theorem; domain-specific theories include algorithmic information theory for lossless compression and rate–distortion theory for lossy compression. These areas of study were essentially created by Claude Shannon, who published fundamental papers on the topic in the late 1940s and early 1950s. Other topics associated with compression include coding theory and statistical inference.

Machine learning
There is a close connection between machine learning and compression. A system that predicts the posterior probabilities of a sequence given its entire history can be used for optimal data compression (by using arithmetic coding on the output distribution). Conversely, an optimal compressor can be used for prediction (by finding the symbol that compresses best, given the previous history). This equivalence has been used as a justification for using data compression as a benchmark for "general intelligence".

An alternative view can show compression algorithms implicitly map strings into implicit feature space vectors, and compression-based similarity measures compute similarity within these feature spaces. For each compressor C(.) we define an associated vector space ℵ, such that C(.) maps an input string x, corresponding to the vector norm ||~x||. An exhaustive examination of the feature spaces underlying all compression algorithms is precluded by space; instead, feature vectors chooses to examine three representative lossless compression methods, LZW, LZ77, and PPM.

According to AIXI theory, a connection more directly explained in Hutter Prize, the best possible compression of x is the smallest possible software that generates x. For example, in that model, a zip file's compressed size includes both the zip file and the unzipping software, since you can not unzip it without both, but there may be an even smaller combined form.

Examples of AI-powered audio/video compression software include NVIDIA Maxine, AIVC. Examples of software that can perform AI-powered image compression include OpenCV, TensorFlow, MATLAB's Image Processing Toolbox (IPT) and High-Fidelity Generative Image Compression.

In unsupervised machine learning, k-means clustering can be utilized to compress data by grouping similar data points into clusters. This technique simplifies handling extensive datasets that lack predefined labels and finds widespread use in fields such as image compression.

Data compression aims to reduce the size of data files, enhancing storage efficiency and speeding up data transmission. K-means clustering, an unsupervised machine learning algorithm, is employed to partition a dataset into a specified number of clusters, k, each represented by the centroid of its points. This process condenses extensive datasets into a more compact set of representative points. Particularly beneficial in image and signal processing, k-means clustering aids in data reduction by replacing groups of data points with their centroids, thereby preserving the core information of the original data while significantly decreasing the required storage space.

Large language models (LLMs) are also capable of lossless data compression, as demonstrated by DeepMind's research with the Chinchilla 70B model. Developed by DeepMind, Chinchilla 70B effectively compressed data, outperforming conventional methods such as Portable Network Graphics (PNG) for images and Free Lossless Audio Codec (FLAC) for audio. It achieved compression of image and audio data to 43.4% and 16.4% of their original sizes, respectively.

Data differencing
Data compression can be viewed as a special case of data differencing. Data differencing consists of producing a difference given a source and a target, with patching reproducing the target given a source and a difference. Since there is no separate source and target in data compression, one can consider data compression as data differencing with empty source data, the compressed file corresponding to a difference from nothing. This is the same as considering absolute entropy (corresponding to data compression) as a special case of relative entropy (corresponding to data differencing) with no initial data.

The term differential compression is used to emphasize the data differencing connection.

Image
Entropy coding originated in the 1940s with the introduction of Shannon–Fano coding, the basis for Huffman coding which was developed in 1950. Transform coding dates back to the late 1960s, with the introduction of fast Fourier transform (FFT) coding in 1968 and the Hadamard transform in 1969.

An important image compression technique is the discrete cosine transform (DCT), a technique developed in the early 1970s. DCT is the basis for JPEG, a lossy compression format which was introduced by the Joint Photographic Experts Group (JPEG) in 1992. JPEG greatly reduces the amount of data required to represent an image at the cost of a relatively small reduction in image quality and has become the most widely used image file format. Its highly efficient DCT-based compression algorithm was largely responsible for the wide proliferation of digital images and digital photos.

Lempel–Ziv–Welch (LZW) is a lossless compression algorithm developed in 1984. It is used in the GIF format, introduced in 1987. DEFLATE, a lossless compression algorithm specified in 1996, is used in the Portable Network Graphics (PNG) format.

Wavelet compression, the use of wavelets in image compression, began after the development of DCT coding. The JPEG 2000 standard was introduced in 2000. In contrast to the DCT algorithm used by the original JPEG format, JPEG 2000 instead uses discrete wavelet transform (DWT) algorithms. JPEG 2000 technology, which includes the Motion JPEG 2000 extension, was selected as the video coding standard for digital cinema in 2004.

Audio
Audio data compression, not to be confused with dynamic range compression, has the potential to reduce the transmission bandwidth and storage requirements of audio data. Audio compression formats compression algorithms are implemented in software as audio codecs. In both lossy and lossless compression, information redundancy is reduced, using methods such as coding, quantization, DCT and linear prediction to reduce the amount of information used to represent the uncompressed data.

Lossy audio compression algorithms provide higher compression and are used in numerous audio applications including Vorbis and MP3. These algorithms almost all rely on psychoacoustics to eliminate or reduce fidelity of less audible sounds, thereby reducing the space required to store or transmit them.

The acceptable trade-off between loss of audio quality and transmission or storage size depends upon the application. For example, one 640 MB compact disc (CD) holds approximately one hour of uncompressed high fidelity music, less than 2 hours of music compressed losslessly, or 7 hours of music compressed in the MP3 format at a medium bit rate. A digital sound recorder can typically store around 200 hours of clearly intelligible speech in 640 MB.

Lossless audio compression produces a representation of digital data that can be decoded to an exact digital duplicate of the original. Compression ratios are around 50–60% of the original size, which is similar to those for generic lossless data compression. Lossless codecs use curve fitting or linear prediction as a basis for estimating the signal. Parameters describing the estimation and the difference between the estimation and the actual signal are coded separately.

A number of lossless audio compression formats exist. See list of lossless codecs for a listing. Some formats are associated with a distinct system, such as Direct Stream Transfer, used in Super Audio CD and Meridian Lossless Packing, used in DVD-Audio, Dolby TrueHD, Blu-ray and HD DVD.

Some audio file formats feature a combination of a lossy format and a lossless correction; this allows stripping the correction to easily obtain a lossy file. Such formats include MPEG-4 SLS (Scalable to Lossless), WavPack, and OptimFROG DualStream.

When audio files are to be processed, either by further compression or for editing, it is desirable to work from an unchanged original (uncompressed or losslessly compressed). Processing of a lossily compressed file for some purpose usually produces a final result inferior to the creation of the same compressed file from an uncompressed original. In addition to sound editing or mixing, lossless audio compression is often used for archival storage, or as master copies.

Lossy audio compression

Lossy audio compression is used in a wide range of applications. In addition to standalone audio-only applications of file playback in MP3 players or computers, digitally compressed audio streams are used in most video DVDs, digital television, streaming media on the Internet, satellite and cable radio, and increasingly in terrestrial radio broadcasts. Lossy compression typically achieves far greater compression than lossless compression, by discarding less-critical data based on psychoacoustic optimizations.

Psychoacoustics recognizes that not all data in an audio stream can be perceived by the human auditory system. Most lossy compression reduces redundancy by first identifying perceptually irrelevant sounds, that is, sounds that are very hard to hear. Typical examples include high frequencies or sounds that occur at the same time as louder sounds. Those irrelevant sounds are coded with decreased accuracy or not at all.

Due to the nature of lossy algorithms, audio quality suffers a digital generation loss when a file is decompressed and recompressed. This makes lossy compression unsuitable for storing the intermediate results in professional audio engineering applications, such as sound editing and multitrack recording. However, lossy formats such as MP3 are very popular with end-users as the file size is reduced to 5-20% of the original size and a megabyte can store about a minute's worth of music at adequate quality.

Several proprietary lossy compression algorithms have been developed that provide higher quality audio performance by using a combination of lossless and lossy algorithms with adaptive bit rates and lower compression ratios. Examples include aptX, LDAC, LHDC, MQA and SCL6.

Coding methods
To determine what information in an audio signal is perceptually irrelevant, most lossy compression algorithms use transforms such as the modified discrete cosine transform (MDCT) to convert time domain sampled waveforms into a transform domain, typically the frequency domain. Once transformed, component frequencies can be prioritized according to how audible they are. Audibility of spectral components is assessed using the absolute threshold of hearing and the principles of simultaneous masking—the phenomenon wherein a signal is masked by another signal separated by frequency—and, in some cases, temporal masking—where a signal is masked by another signal separated by time. Equal-loudness contours may also be used to weigh the perceptual importance of components. Models of the human ear-brain combination incorporating such effects are often called psychoacoustic models.

Other types of lossy compressors, such as the linear predictive coding (LPC) used with speech, are source-based coders. LPC uses a model of the human vocal tract to analyze speech sounds and infer the parameters used by the model to produce them moment to moment. These changing parameters are transmitted or stored and used to drive another model in the decoder which reproduces the sound.

Lossy formats are often used for the distribution of streaming audio or interactive communication (such as in cell phone networks). In such applications, the data must be decompressed as the data flows, rather than after the entire data stream has been transmitted. Not all audio codecs can be used for streaming applications.

Latency is introduced by the methods used to encode and decode the data. Some codecs will analyze a longer segment, called a frame, of the data to optimize efficiency, and then code it in a manner that requires a larger segment of data at one time to decode. The inherent latency of the coding algorithm can be critical; for example, when there is a two-way transmission of data, such as with a telephone conversation, significant delays may seriously degrade the perceived quality.

In contrast to the speed of compression, which is proportional to the number of operations required by the algorithm, here latency refers to the number of samples that must be analyzed before a block of audio is processed. In the minimum case, latency is zero samples (e.g., if the coder/decoder simply reduces the number of bits used to quantize the signal). Time domain algorithms such as LPC also often have low latencies, hence their popularity in speech coding for telephony. In algorithms such as MP3, however, a large number of samples have to be analyzed to implement a psychoacoustic model in the frequency domain, and latency is on the order of 23 ms.

Speech encoding
Speech encoding is an important category of audio data compression. The perceptual models used to estimate what aspects of speech a human ear can hear are generally somewhat different from those used for music. The range of frequencies needed to convey the sounds of a human voice is normally far narrower than that needed for music, and the sound is normally less complex. As a result, speech can be encoded at high quality using a relatively low bit rate.

This is accomplished, in general, by some combination of two approaches:
 * Only encoding sounds that could be made by a single human voice.
 * Throwing away more of the data in the signal—keeping just enough to reconstruct an "intelligible" voice rather than the full frequency range of human hearing.

The earliest algorithms used in speech encoding (and audio data compression in general) were the A-law algorithm and the μ-law algorithm.

History

Early audio research was conducted at Bell Labs. There, in 1950, C. Chapin Cutler filed the patent on differential pulse-code modulation (DPCM). In 1973, Adaptive DPCM (ADPCM) was introduced by P. Cummiskey, Nikil S. Jayant and James L. Flanagan.

Perceptual coding was first used for speech coding compression, with linear predictive coding (LPC). Initial concepts for LPC date back to the work of Fumitada Itakura (Nagoya University) and Shuzo Saito (Nippon Telegraph and Telephone) in 1966. During the 1970s, Bishnu S. Atal and Manfred R. Schroeder at Bell Labs developed a form of LPC called adaptive predictive coding (APC), a perceptual coding algorithm that exploited the masking properties of the human ear, followed in the early 1980s with the code-excited linear prediction (CELP) algorithm which achieved a significant compression ratio for its time. Perceptual coding is used by modern audio compression formats such as MP3 and AAC.

Discrete cosine transform (DCT), developed by Nasir Ahmed, T. Natarajan and K. R. Rao in 1974, provided the basis for the modified discrete cosine transform (MDCT) used by modern audio compression formats such as MP3, Dolby Digital, and AAC. MDCT was proposed by J. P. Princen, A. W. Johnson and A. B. Bradley in 1987, following earlier work by Princen and Bradley in 1986.

The world's first commercial broadcast automation audio compression system was developed by Oscar Bonello, an engineering professor at the University of Buenos Aires. In 1983, using the psychoacoustic principle of the masking of critical bands first published in 1967, he started developing a practical application based on the recently developed IBM PC computer, and the broadcast automation system was launched in 1987 under the name Audicom. 35 years later, almost all the radio stations in the world were using this technology manufactured by a number of companies because the inventor refuses to get invention patents for his work. He prefers declaring it of Public Domain publishing it

A literature compendium for a large variety of audio coding systems was published in the IEEE's Journal on Selected Areas in Communications (JSAC), in February 1988. While there were some papers from before that time, this collection documented an entire variety of finished, working audio coders, nearly all of them using perceptual techniques and some kind of frequency analysis and back-end noiseless coding.

Video
Uncompressed video requires a very high data rate. Although lossless video compression codecs perform at a compression factor of 5 to 12, a typical H.264 lossy compression video has a compression factor between 20 and 200.

The two key video compression techniques used in video coding standards are the DCT and motion compensation (MC). Most video coding standards, such as the H.26x and MPEG formats, typically use motion-compensated DCT video coding (block motion compensation).

Most video codecs are used alongside audio compression techniques to store the separate but complementary data streams as one combined package using so-called container formats.

Encoding theory
Video data may be represented as a series of still image frames. Such data usually contains abundant amounts of spatial and temporal redundancy. Video compression algorithms attempt to reduce redundancy and store information more compactly.

Most video compression formats and codecs exploit both spatial and temporal redundancy (e.g. through difference coding with motion compensation). Similarities can be encoded by only storing differences between e.g. temporally adjacent frames (inter-frame coding) or spatially adjacent pixels (intra-frame coding). Inter-frame compression (a temporal delta encoding) (re)uses data from one or more earlier or later frames in a sequence to describe the current frame. Intra-frame coding, on the other hand, uses only data from within the current frame, effectively being still-image compression.

The intra-frame video coding formats used in camcorders and video editing employ simpler compression that uses only intra-frame prediction. This simplifies video editing software, as it prevents a situation in which a compressed frame refers to data that the editor has deleted.

Usually, video compression additionally employs lossy compression techniques like quantization that reduce aspects of the source data that are (more or less) irrelevant to the human visual perception by exploiting perceptual features of human vision. For example, small differences in color are more difficult to perceive than are changes in brightness. Compression algorithms can average a color across these similar areas in a manner similar to those used in JPEG image compression. As in all lossy compression, there is a trade-off between video quality and bit rate, cost of processing the compression and decompression, and system requirements. Highly compressed video may present visible or distracting artifacts.

Other methods other than the prevalent DCT-based transform formats, such as fractal compression, matching pursuit and the use of a discrete wavelet transform (DWT), have been the subject of some research, but are typically not used in practical products. Wavelet compression is used in still-image coders and video coders without motion compensation. Interest in fractal compression seems to be waning, due to recent theoretical analysis showing a comparative lack of effectiveness of such methods.

Inter-frame coding
In inter-frame coding, individual frames of a video sequence are compared from one frame to the next, and the video compression codec records the differences to the reference frame. If the frame contains areas where nothing has moved, the system can simply issue a short command that copies that part of the previous frame into the next one. If sections of the frame move in a simple manner, the compressor can emit a (slightly longer) command that tells the decompressor to shift, rotate, lighten, or darken the copy. This longer command still remains much shorter than data generated by intra-frame compression. Usually, the encoder will also transmit a residue signal which describes the remaining more subtle differences to the reference imagery. Using entropy coding, these residue signals have a more compact representation than the full signal. In areas of video with more motion, the compression must encode more data to keep up with the larger number of pixels that are changing. Commonly during explosions, flames, flocks of animals, and in some panning shots, the high-frequency detail leads to quality decreases or to increases in the variable bitrate.

Hybrid block-based transform formats

Many commonly used video compression methods (e.g., those in standards approved by the ITU-T or ISO) share the same basic architecture that dates back to H.261 which was standardized in 1988 by the ITU-T. They mostly rely on the DCT, applied to rectangular blocks of neighboring pixels, and temporal prediction using motion vectors, as well as nowadays also an in-loop filtering step.

In the prediction stage, various deduplication and difference-coding techniques are applied that help decorrelate data and describe new data based on already transmitted data.

Then rectangular blocks of remaining pixel data are transformed to the frequency domain. In the main lossy processing stage, frequency domain data gets quantized in order to reduce information that is irrelevant to human visual perception.

In the last stage statistical redundancy gets largely eliminated by an entropy coder which often applies some form of arithmetic coding.

In an additional in-loop filtering stage various filters can be applied to the reconstructed image signal. By computing these filters also inside the encoding loop they can help compression because they can be applied to reference material before it gets used in the prediction process and they can be guided using the original signal. The most popular example are deblocking filters that blur out blocking artifacts from quantization discontinuities at transform block boundaries.

History
In 1967, A.H. Robinson and C. Cherry proposed a run-length encoding bandwidth compression scheme for the transmission of analog television signals. The DCT, which is fundamental to modern video compression, was introduced by Nasir Ahmed, T. Natarajan and K. R. Rao in 1974.

H.261, which debuted in 1988, commercially introduced the prevalent basic architecture of video compression technology. It was the first video coding format based on DCT compression. H.261 was developed by a number of companies, including Hitachi, PictureTel, NTT, BT and Toshiba.

The most popular video coding standards used for codecs have been the MPEG standards. MPEG-1 was developed by the Motion Picture Experts Group (MPEG) in 1991, and it was designed to compress VHS-quality video. It was succeeded in 1994 by MPEG-2/H.262, which was developed by a number of companies, primarily Sony, Thomson and Mitsubishi Electric. MPEG-2 became the standard video format for DVD and SD digital television. In 1999, it was followed by MPEG-4/H.263. It was also developed by a number of companies, primarily Mitsubishi Electric, Hitachi and Panasonic.

H.264/MPEG-4 AVC was developed in 2003 by a number of organizations, primarily Panasonic, Godo Kaisha IP Bridge and LG Electronics. AVC commercially introduced the modern context-adaptive binary arithmetic coding (CABAC) and context-adaptive variable-length coding (CAVLC) algorithms. AVC is the main video encoding standard for Blu-ray Discs, and is widely used by video sharing websites and streaming internet services such as YouTube, Netflix, Vimeo, and iTunes Store, web software such as Adobe Flash Player and Microsoft Silverlight, and various HDTV broadcasts over terrestrial and satellite television.

Genetics
Genetics compression algorithms are the latest generation of lossless algorithms that compress data (typically sequences of nucleotides) using both conventional compression algorithms and genetic algorithms adapted to the specific datatype. In 2012, a team of scientists from Johns Hopkins University published a genetic compression algorithm that does not use a reference genome for compression. HAPZIPPER was tailored for HapMap data and achieves over 20-fold compression (95% reduction in file size), providing 2- to 4-fold better compression and is less computationally intensive than the leading general-purpose compression utilities. For this, Chanda, Elhaik, and Bader introduced MAF-based encoding (MAFE), which reduces the heterogeneity of the dataset by sorting SNPs by their minor allele frequency, thus homogenizing the dataset. Other algorithms developed in 2009 and 2013 (DNAZip and GenomeZip) have compression ratios of up to 1200-fold—allowing 6 billion basepair diploid human genomes to be stored in 2.5 megabytes (relative to a reference genome or averaged over many genomes). For a benchmark in genetics/genomics data compressors, see

Outlook and currently unused potential
It is estimated that the total amount of data that is stored on the world's storage devices could be further compressed with existing compression algorithms by a remaining average factor of 4.5:1. It is estimated that the combined technological capacity of the world to store information provides 1,300 exabytes of hardware digits in 2007, but when the corresponding content is optimally compressed, this only represents 295 exabytes of Shannon information.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Data compression


text:
History of the Democratic Republic of the Congo

The earliest known human settlements in what is now the Democratic Republic of the Congo have been dated back to the Middle Stone Age, approximately 90,000 years ago. The first real states, such as the Kongo, the Lunda, the Luba and Kuba, appeared south of the equatorial forest on the savannah from the 14th century onwards.

The Kingdom of Kongo controlled much of western and central Africa including what is now the western portion of the DR Congo between the 14th and the early 19th centuries. At its peak it had many as 500,000 people, and its capital was known as Mbanza-Kongo (south of Matadi, in modern-day Angola). In the late 15th century, Portuguese sailors arrived in the Kingdom of Kongo, and this led to a period of great prosperity and consolidation, with the king's power being founded on Portuguese trade. King Afonso I (1506–1543) had raids carried out on neighboring districts in response to Portuguese requests for slaves. After his death, the kingdom underwent a deep crisis.

The Atlantic slave trade occurred from approximately 1500 to 1850, with the entire west coast of Africa targeted, but the region around the mouth of the Congo suffered the most intensive enslavement. Over a strip of coastline about 400 km long, about 4 million people were enslaved and sent across the Atlantic to sugar plantations in Brazil, the US and the Caribbean. From 1780 onwards, there was a higher demand for slaves in the US which led to more people being enslaved. By 1780, more than 15,000 people were shipped annually from the Loango Coast, north of the Congo.

In 1870, explorer Henry Morton Stanley arrived in and explored what is now the DR Congo. Belgian colonization of DR Congo began in 1885 when King Leopold II founded and ruled the Congo Free State. However, de facto control of such a huge area took decades to achieve. Many outposts were built to extend the power of the state over such a vast territory. In 1885, the Force Publique was set up, a colonial army with white officers and black soldiers. In 1886, Leopold made Camille Jansen the first Belgian governor-general of Congo. Over the late 19th century, various Christian (including Catholic and Protestant) missionaries arrived intending to convert the local population. A railway between Matadi and Stanley Pool was built in the 1890s. Reports of widespread murder, torture, and other abuses in the rubber plantations led to international and Belgian outrage and the Belgian government transferred control of the region from Leopold II and established the Belgian Congo in 1908.

Following unrest, Belgium granted Congo independence in 1960. However, the Congo remained unstable, leading to the Congo Crisis, where the regional governments of Katanga and South Kasai attempted to gain independence with Belgian support. Prime Minister Patrice Lumumba tried to suppress secession with the aid of the Soviet Union as part of the Cold War, causing the United States to support a coup led by Colonel Joseph Mobutu. Lumumba was handed over to the Katangan government and executed in 1961. The secessionist movements were later defeated by the Congolese government as were the Soviet-backed Simba rebels. Following the end of the Congo Crisis in 1965, Joseph Kasa-Vubu was deposed and Mobutu seized complete power of the country and then renamed it Zaire. He sought to Africanize the country, changing his own name to Mobutu Sese Seko Kuku Ngbendu Wa Za Banga, and demanded that African citizens change their Western names to traditional African names. Mobutu sought to repress any opposition to his rule, which he successfully did throughout the 1980s. However, with his regime weakened in the 1990s, Mobutu was forced to agree to a power-sharing government with the opposition party. Mobutu remained the head of state and promised elections within the next two years that never took place.

During the First Congo War, Rwanda invaded Zaire, in which Mobutu lost his power during this process. In 1997, Laurent-Désiré Kabila took power and renamed the country the Democratic Republic of the Congo. Afterwards, the Second Congo War broke out, resulting in a regional war in which many different African nations took part and in which millions of people were killed or displaced. Laurent-Désiré Kabila was assassinated by his own bodyguard in 2001, and his son, Joseph, succeeded him and was later elected president by the Congolese government in 2006. Joseph Kabila quickly sought peace. Foreign soldiers remained in the Congo for a few years and a power-sharing government between Joseph Kabila and the opposition party was set up. Joseph Kabila later resumed complete control over the Congo and was re-elected in a disputed election in 2011. In 2018, Félix Tshisekedi was elected president; in the first peaceful transfer of power since independence.

Early history
The area now known as the Democratic Republic of the Congo was populated as early as 90,000 years ago, as shown by the 1988 discovery of the Semliki harpoon at Katanda, one of the oldest barbed harpoons ever found, which is believed to have been used to catch giant river catfish.

The Kingdom of Kongo existed from the 14th to the early 19th century. Until the arrival of the Portuguese it was the dominant force in the region along with the Kingdom of Luba, the Kingdom of Lunda, the Mongo people and the Anziku Kingdom.

Congo Free State (1885–1908)
The Congo Free State was a privately controlled by Leopold II of Belgium through the Association Internationale africaine, a non-governmental organization. Leopold was the sole shareholder and chairman. The state included the entire area of the present the Democratic Republic of the Congo. Under Leopold II, the Congo Free State became one of the most infamous international scandals of the turn of the twentieth century. The report of the British Consul Roger Casement led to the arrest and punishment of white officials who had been responsible for cold-blooded killings during a rubber-collecting expedition in 1900, including a Belgian national who caused the shooting of at least 122 Congolese natives. Estimates of the total death toll vary considerably. The first census was only done in 1924, so it is even more difficult to quantify the population loss of the period. Roger Casement's famous 1904 report estimated ten million people. According to Casement's report, indiscriminate "war", starvation, reduction of births and Tropical diseases caused the country's depopulation. European and U.S. press agencies exposed the conditions in the Congo Free State to the public in 1900. By 1908 public and diplomatic pressure had led Leopold II to annex the Congo as the Belgian Congo colony.

Belgian Congo (1908–60)
On 15 November 1908 King Leopold II of Belgium formally relinquished personal control of the Congo Free State. The renamed Belgian Congo was put under the direct administration of the Belgian government and its Ministry of Colonies.

Belgian rule in the Congo was based around the "colonial trinity" (trinité colonial) of state, missionary and private company interests. The privileging of Belgian commercial interests meant that large amounts of capital flowed into the Congo and that individual regions became specialized. The interests of the government and private enterprise became closely tied; the state helped companies break strikes and remove other barriers imposed by the indigenous population. The country was split into nesting, hierarchically organized administrative subdivisions, and run uniformly according to a set "native policy" (politique indigène)—in contrast to the British and the French, who generally favored the system of indirect rule whereby traditional leaders were retained in positions of authority under colonial oversight. There was also a high degree of racial segregation. Large numbers of white immigrants who moved to the Congo after the end of World War II came from across the social spectrum, but were nonetheless always treated as superior to blacks.

During the 1940s and 1950s, the Congo experienced an unprecedented level of urbanization and the colonial administration began various development programs aimed at making the territory into a "model colony". Notable advances were made in treating diseases such as African trypanosomiasis. One of the results of these measures was the development of a new middle class of Europeanised African évolués in the cities. By the 1950s the Congo had a wage labor force twice as large as that in any other African colony. The Congo's rich natural resources, including uranium—much of the uranium used by the U.S. nuclear programme during World War II was Congolese—led to substantial interest in the region from both the Soviet Union and the United States as the Cold War developed.

Rise in Congolese political activity
During the latter stages of World War II a new social stratum emerged in the Congo, known as the évolués. Forming an African middle class in the colony, they held skilled positions (such as clerks and nurses) made available by the economic boom. While there were no universal criteria for determining évolué status, it was generally accepted that one would have "a good knowledge of French, adhere to Christianity, and have some form of post-primary education." Early on in their history, évolués sought to use their unique status to earn special privileges in the Congo. Since opportunities for upward mobility through the colonial structure were limited, the évolué class institutionally manifested itself in elite clubs through which they could enjoy trivial privileges that made them feel distinct from the Congolese "masses". Additional groups, such as labor unions, alumni associations, and ethnic syndicates, provided other Congolese the means of organization. Among the most important of these was the Alliance des Bakongo (ABAKO), representing the Kongo people of the Lower Congo. However, they were restricted in their actions by the administration. While white settlers were consulted in the appointment of certain officials, the Congolese had no means of expressing their beliefs through the governing structures. Though native chiefs held legal authority in some jurisdictions, in practice they were used by the administration to further its own policies.

Up into the 1950s, most évolués were concerned only with social inequalities and their treatment by the Belgians. Questions of self-government were not considered until 1954 when ABAKO requested that the administration consider a list of suggested candidates for a Léopoldville municipal post. That year the association was taken over by Joseph Kasa-Vubu, and under his leadership, it became increasingly hostile to the colonial authority and sought autonomy for the Kongo regions in the Lower Congo. In 1956 a group of Congolese intellectuals under the tutelage of several European academics issued a manifesto calling for a transition to independence over the course of 30 years. The ABAKO quickly responded with a demand for "immediate independence". The Belgian government was not prepared to grant the Congo independence and even when it started realizing the necessity of a plan for decolonization in 1957, it was assumed that such a process would be solidly controlled by Belgium. In December 1957 the colonial administration instituted reforms that permitted municipal elections and the formation of political parties. Some Belgian parties attempted to establish branches in the colony, but these were largely ignored by the population in favour of Congolese-initiated groups. Nationalism fermented in 1958 as more évolués began interacting with others outside of their own locales and started discussing the future structures of a post-colonial Congolese state. Nevertheless, most political mobilisation occurred along tribal and regional divisions. In Katanga, various tribal groups came together to form the Confédération des associations tribales du Katanga (CONAKAT) under the leadership of Godefroid Munongo and Moïse Tshombe. Hostile to immigrant peoples, it advocated provincial autonomy and close ties with Belgium. Most of its support was rooted in individual chiefs, businessmen, and European settlers of southern Katanga. It was opposed by Jason Sendwe's Association Générale des Baluba du Katanga (BALUBAKAT).

In October 1958 a group of Léopoldville évolués including Patrice Lumumba, Cyrille Adoula and Joseph Iléo established the Mouvement National Congolais (MNC). Diverse in membership, the party sought to peacefully achieve Congolese independence, promote the political education of the populace, and eliminate regionalism. The MNC drew most of its membership from the residents of the eastern city of Stanleyville, where Lumumba was well known, and from the population of the Kasai Province, where efforts were directed by a Muluba businessman, Albert Kalonji. Belgian officials appreciated its moderate and anti-separatist stance and allowed Lumumba to attend the All-African Peoples' Conference in Accra, Ghana, in December 1958 (Kasa-Vubu was informed that the documents necessary for his travel to the event were not in order and was not permitted to go). Lumumba was deeply impressed by the Pan-Africanist ideals of Ghanaian President Kwame Nkrumah and returned to the Congo with a more radical party programme. He reported on his trip during a widely attended rally in Léopoldville and demanded the country's "genuine" independence.

Fearing that they were being overshadowed by Lumumba and the MNC, Kasa-Vubu and the ABAKO leadership announced that they would be hosting their own rally in the capital on 4 January 1959. The municipal government (under Belgian domination) was given short notice, and communicated that only a "private meeting" would be authorised. On the scheduled day of the rally the ABAKO leadership told the crowd that had gathered that the event was postponed and that they should disperse. The mass was infuriated and instead began hurling stones at the police and pillaging European property, initiating three days of violent and destructive riots. The Force Publique, the colonial army, was called into service and suppressed the revolt with considerable brutality. In wake of the riots Kasa-Vubu and his lieutenants were arrested. Unlike earlier expressions of discontent, the grievances were conveyed primarily by uneducated urban residents, not évolués. Popular opinion in Belgium was one of extreme shock and surprise. An investigative commission found the riots to be the culmination of racial discrimination, overcrowding, unemployment, and wishes for more political self-determination. On 13 January the administration announced several reforms, and the Belgian King, Baudouin, declared that independence would be granted to the Congo in the future.

Meanwhile, discontent surfaced among the MNC leadership, who were bothered by Lumumba's domination over the party's politics. Relations between Lumumba and Kalonji also grew tense, as the former was upset with how the latter was transforming the Kasai branch into an exclusively Luba group and antagonising other tribes. This culminated into the split of the party into the MNC-Lumumba/MNC-L under Lumumba and the MNC-Kalonji/MNC-K under Kalonji and Iléo. The latter began advocating federalism. Adoula left the organisation. Alone to lead his own faction and facing competition from ABAKO, Lumumba became increasingly insistent in his demands for independence. Following an October riot in Stanleyville he was arrested. Nevertheless, the influence of himself and the MNC-L continued to grow rapidly. The party advocated for a strong unitary state, nationalism, and the termination of Belgian rule and began forming alliances with regional groups, such as the Kivu-based Centre du Regroupement Africain (CEREA). Though the Belgians supported a unitary system over the federal models suggested by ABAKO and CONAKAT, they and more moderate Congolese were unnerved by Lumumba's increasingly extremist attitudes. With the implicit support of the colonial administration, the moderates formed the Parti National du Progrès (PNP) under the leadership of Paul Bolya and Albert Delvaux. It advocated centralisation, respect for traditional elements, and close ties with Belgium. In southern Léopoldville Province, a socialist-federalist party, the Parti Solidaire Africain (PSA) was founded. Antoine Gizenga served as its president, and Cléophas Kamitatu was in charge of the Léopoldville Province chapter.

Independence and the Congo Crisis (1960–65)
Following the riots in Leopoldville (4–7 January 1959) and in Stanleyville (31 October 1959), the Belgians realised they could not maintain control of such a vast country in the face of rising demands for independence. Belgian and Congolese political leaders held a Round Table Conference in Brussels beginning on 18 January 1960.

At the end of the conference, on 27 January 1960, it was announced that elections would be held in the Congo on 22 May 1960, and full independence granted on 30 June 1960. The elections produced the nationalist Patrice Lumumba as prime minister, and Joseph Kasavubu as president. On independence the country adopted the name "Republic of the Congo" (République du Congo). The French colony of Middle Congo (Moyen Congo) also chose the name Republic of the Congo upon its independence, so the two countries were more commonly known as Congo-Léopoldville and Congo-Brazzaville, after their capital cities.

In 1960, the country was very unstable—regional tribal leaders held far more power than the central government—and with the departure of the Belgian administrators, almost no skilled bureaucrats remained in the country. The first Congolese graduated from university only in 1956, and very few in the new nation had any idea how to manage a country of such size.

On 5 July 1960, a military mutiny by Congolese soldiers against their European officers broke out in the capital and rampant looting began. On 11 July 1960 the richest province of the country, Katanga, seceded under Moise Tshombe. The United Nations sent 20,000 peacekeepers to protect Europeans in the country and try to restore order. Western paramilitaries and mercenaries, often hired by mining companies to protect their interests, also began to pour into the country. In this period Congo's second richest province, Kasai, also announced its independence on 8 August 1960.

After trying to get help from the United States and the United Nations, Prime Minister Lumumba turned to the USSR for assistance. Nikita Khrushchev agreed to help, offering advanced weaponry and technical advisors. The United States viewed the Soviet presence as an attempt to take advantage of the situation and gain a proxy state in sub-Saharan Africa. UN forces were ordered to block any shipments of arms into the country. The United States also looked for a way to replace Lumumba as leader. President Kasavubu had clashed with Prime Minister Lumumba and advocated an alliance with the West rather than the Soviets. The U.S. sent weapons and CIA personnel to aid forces allied with Kasavubu and combat the Soviet presence.

On 23 August, the Congolese armed forces invaded South Kasai and perpetrated massacres against the Luba people. Lumumba was dismissed from office on 5 September 1960 by Kasavubu who publicly blamed him for the massacres in South Kasai and for involving Soviets in the country. On 14 September 1960, with CIA support, Colonel Joseph Mobutu overthrew the government and arrested Lumumba. A technocratic government, the College of Commissioners-General, was established.

On 17 January 1961 Mobutu sent Lumumba to Élisabethville (now Lubumbashi), capital of Katanga. In full view of the press he was beaten and forced to eat copies of his own speeches. For three weeks afterward, he was not seen or heard from. Then Katangan radio announced implausibly that he had escaped and been killed by villagers. It was soon clear that in fact he had been tortured and killed along with two others shortly after his arrival. In 2001, a Belgian inquiry established that he had been shot by Katangan gendarmes in the presence of Belgian officers, under Katangan command. Lumumba was beaten, placed in front of a firing squad with two allies, cut up, buried, dug up and what remained was dissolved in acid.

In Stanleyville, those loyal to the deposed Lumumba set up a rival government under Antoine Gizenga which lasted from 31 March 1961 until it was reintegrated on 5 August 1961. After some reverses, UN and Congolese government forces succeeded in recapturing the breakaway provinces of South Kasai on 30 December 1961, and Katanga on 15 January 1963.

Beginning in 1964, in the east of the country, Soviet and Cuban backed rebels called the Simbas rose up, taking a significant amount of territory and proclaiming a communist "People's Republic of the Congo" in Stanleyville. As the Congolese government was reclaiming territory from the Simbas, the rebels resorted to taking the local white population hostage. Belgian and American forces pushed the Simbas out of Stanleyville in November 1964 during a hostage rescue operation. Congolese government forces, supported by European mercenaries, fully defeated the Simba rebels by November 1965. The Simba rebels executed 20,000 Congolese and 392 Western hostages, including 268 Belgians, during the rebellion. Tens of thousands of people were killed in total during the suppression of the Simbas.

Zaire (1965–1997)
Unrest and rebellion plagued the government until November 1965, when Lieutenant General Joseph-Désiré Mobutu, by then commander in chief of the national army, seized control of the country and declared himself president for the next five years. Mobutu quickly consolidated his power, despite the Stanleyville mutinies of 1966 and 1967, and was elected unopposed as president in a sham election in 1970 for a seven-year term.

Embarking on a campaign of cultural awareness, President Mobutu renamed the country the "Republic of Zaire" in 1971 and required citizens to adopt African names and drop their French-language ones. The name comes from Portuguese, adapted from the Kongo word nzere or nzadi ("river that swallows all rivers"). Among other changes, Leopoldville became Kinshasa and Katanga Shaba.

Relative peace and stability prevailed until 1977 and 1978 when Katangan Front for Congolese National Liberation rebels, based in the Angolan People's Republic, launched the Shaba I and II invasions into the southeast Shaba region. These rebels were driven out with the aid of French and Belgian paratroopers plus Moroccan troops. An Inter-African Force remained in the region for some time afterwards.

Zaire remained a one-party state in the 1980s. Although Mobutu successfully maintained control during this period, opposition parties, most notably the Union pour la Démocratie et le Progrès Social (UDPS), were active. Mobutu's attempts to quell these groups drew significant international criticism.

As the Cold War came to a close, internal and external pressures on Mobutu increased. In late 1989 and early 1990, Mobutu was weakened by a series of domestic protests, by heightened international criticism of his regime's human rights practices, by a faltering economy, and by government corruption, most notably his own massive embezzlement of government funds for personal use.

In April 1990, Mobutu declared the Third Republic, agreeing to a limited multi-party system with free elections and a constitution. As details of the reforms were delayed, soldiers in September 1991 began looting Kinshasa to protest their unpaid wages. Two thousand French and Belgian troops, some of whom were flown in on U.S. Air Force planes, arrived to evacuate the 20,000 endangered foreign nationals in Kinshasa.

In 1992, after previous similar attempts, the long-promised Sovereign National Conference was staged, encompassing over 2,000 representatives from various political parties. The conference gave itself a legislative mandate and elected Archbishop Laurent Monsengwo Pasinya as its chairman, along with Étienne Tshisekedi, leader of the UDPS, as prime minister. By the end of the year Mobutu had created a rival government with its own prime minister. The ensuing stalemate produced a compromise merger of the two governments into the High Council of Republic-Parliament of Transition (HCR-PT) in 1994, with Mobutu as head of state and Kengo Wa Dondo as prime minister. Although presidential and legislative elections were scheduled repeatedly over the next two years, they never took place.

First Congo War (1996–97)
By 1996, tensions from the war and genocide in neighboring Rwanda had spilled over into Zaire. Rwandan Hutu militia forces (Interahamwe) who had fled Rwanda following the ascension of a Tutsi-led government had been using Hutu refugee camps in eastern Zaire as bases for incursions into Rwanda. In October 1996 Rwandan forces attacked refugee camps in the Ruzizi Plain near the intersection of the Congolese, Rwandan and Burundi borders meet, scattering refugees. They took Uvira, then Bukavu, Goma and Mugunga.

Hutu militia forces soon allied with the Zairian armed forces (FAZ) to launch a campaign against Congolese ethnic Tutsis in eastern Zaire. In turn, these Tutsis formed a militia to defend themselves against attacks. When the Zairian government began to escalate the massacres in November 1996, Tutsi militias erupted in rebellion against Mobutu.

The Tutsi militia was soon joined by various opposition groups and supported by several countries, including Rwanda and Uganda. This coalition, led by Laurent-Desire Kabila, became known as the Alliance des Forces Démocratiques pour la Libération du Congo-Zaïre (AFDL). The AFDL, now seeking the broader goal of ousting Mobutu, made significant military gains in early 1997. Various Zairean politicians who had unsuccessfully opposed the dictatorship of Mobutu for many years now saw an opportunity for them in the invasion of Zaire by two of the region's strongest military forces. Following failed peace talks between Mobutu and Kabila in May 1997, Mobutu left the country on 16 May. The AFDL entered Kinshasa unopposed a day later, and Kabila named himself president, reverting the name of the country to the Democratic Republic of the Congo. He marched into Kinshasa on 20 May and consolidated power around himself and the AFDL.

In September 1997, Mobutu died in exile in Morocco.

Second Congo War (1998–2003)
Kabila demonstrated little ability to manage the problems of his country, and lost his allies. To counterbalance the power and influence of Rwanda in DRC, Ugandan troops created another rebel movement called the Movement for the Liberation of Congo (MLC), led by the Congolese warlord Jean-Pierre Bemba. They attacked in August 1998, backed by Rwandan and Ugandan troops. Soon afterwards, Angola, Namibia, and Zimbabwe became involved militarily in the Congo, with Angola and Zimbabwe supporting the government. While the six African governments involved in the war signed a ceasefire accord in Lusaka in July 1999, the Congolese rebels did not and the ceasefire broke down within months.

Kabila was assassinated in 2001 by a bodyguard called Rashidi Kasereka, 18, who was then shot dead, according to Justice Minister Mwenze Kongolo. Another account of the assassination says that the real killer escaped.

Kabila was succeeded by his son, Joseph. Upon taking office, Kabila called for multilateral peace talks to end the war. Kabila partly succeeded when a further peace deal was brokered between him, Uganda, and Rwanda leading to the apparent withdrawal of foreign troops.

Currently, the Ugandans and the MLC still hold a 200 mi wide section of the north of the country; Rwandan forces and its front, the Rassemblement Congolais pour la Démocratie (RCD) control a large section of the east; and government forces or their allies hold the west and south of the country. There were reports that the conflict is being prolonged as a cover for extensive looting of the substantial natural resources in the country, including diamonds, copper, zinc, and coltan. The conflict was reignited in January 2002 by ethnic clashes in the northeast and both Uganda and Rwanda then halted their withdrawal and sent in more troops. Talks between Kabila and the rebel leaders, held in Sun City, lasted a full six weeks, beginning in April 2002. In June, they signed a peace accord under which Kabila would share power with former rebels. By June 2003, all foreign armies except those of Rwanda had pulled out of Congo.

Few people in the Congo have been unaffected by the conflict. A survey conducted in 2009 by the ICRC and Ipsos shows that three-quarters (76%) of the people interviewed have been affected in some way–either personally or due to the wider consequences of armed conflict.

The response of the international community has been incommensurate with the scale of the disaster resulting from the war in the Congo. Its support for political and diplomatic efforts to end the war has been relatively consistent, but it has taken no effective steps to abide by repeated pledges to demand accountability for the war crimes and crimes against humanity that were routinely committed in Congo. The United Nations Security Council and the U.N. Secretary-General have frequently denounced human rights abuses and the humanitarian disaster that the war unleashed on the local population, but have shown little will to tackle the responsibility of occupying powers for the atrocities taking place in areas under their control, areas where the worst violence in the country took place. In particular Rwanda and Uganda have escaped any significant sanction for their role.

Transitional government (2003–2006)
DR Congo had a transitional government in July 2003 until the election was over. A constitution was approved by voters and on 30 July 2006 the Congo held its first multi-party elections since independence in 1960. Joseph Kabila took 45% of the votes and his opponent Jean-Pierre Bemba 20%. That was the origin of a fight between the two parties from 20 to 22 August 2006 in the streets of the capital, Kinshasa. Sixteen people died before policemen and MONUC took control of the city. A new election was held on 29 October 2006, which Kabila won with 70% of the vote. Bemba has decried election "irregularities". On 6 December 2006 Joseph Kabila was sworn in as president.

Kabila overstays his term
In December 2011, Joseph Kabila was re-elected for a second term as president. After the results were announced on 9 December, there was violent unrest in Kinshasa and Mbuji-Mayi, where official tallies showed that a strong majority had voted for the opposition candidate Étienne Tshisekedi. Official observers from the Carter Center reported that returns from almost 2,000 polling stations in areas where support for Tshisekedi was strong had been lost and not included in the official results. They described the election as lacking credibility. On 20 December, Kabila was sworn in for a second term, promising to invest in infrastructure and public services. However, Tshisekedi maintained that the result of the election was illegitimate and said that he intended also to "swear himself in" as president.

On 19 January 2015 protests led by students at the University of Kinshasa broke out. The protests began following the announcement of a proposed law that would allow Kabila to remain in power until a national census can be conducted (elections had been planned for 2016). By Wednesday 21 January clashes between police and protesters had claimed at least 42 lives (although the government claimed only 15 people had been killed).

Similarly, in September 2016, violent protests were met with brutal force by the police and Republican Guard soldiers. Opposition groups claim 80 dead, including the Students' Union leader. From Monday 19 September Kinshasa residents, as well as residents elsewhere in Congo, were mostly confined to their homes. Police arrested anyone remotely connected to the opposition as well as innocent onlookers. Government propaganda, on television, and actions of covert government groups in the streets, acted against opposition as well as foreigners. The president's mandate was due to end on 19 December 2016, but no plans were made to elect a replacement at that time and this caused further protests.

Félix Tshisekedi presidency (2019–present)
On 30 December 2018 the presidential election to determine the successor to Kabila was held. On 10 January 2019, the electoral commission announced opposition candidate Félix Tshisekedi as the winner of the vote. He was officially sworn in as president on 24 January 2019. in the ceremony of taking of the office Félix Tshisekedi appointed Vital Kamerhe as his chief of staff. In June 2020, chief of staff Vital Kamerhe was found guilty of embezzling public funds and he was sentenced to 20 years in prison. However, Kamerhe was released in December 2021.

The political allies of former president Joseph Kabila, who stepped down in January 2019, maintained control of key ministries, the legislature, judiciary and security services. However, President Felix Tshisekedi succeeded to strengthen his hold on power. In a series of moves, he won over more legislators, gaining the support of almost 400 out of 500 members of the National Assembly. The pro-Kabila speakers of both houses of parliament were forced out. In April 2021, the new government was formed without the supporters of Kabila. President Felix Tshisekedi succeeded to oust the last remaining elements of his government who were loyal to former leader Joseph Kabila. In January 2021, DRC's President Félix Tshisekedi pardoned all those convicted in the murder of Laurent-Désiré Kabila in 2001. Colonel Eddy Kapend and his co-defendants, who have been incarcerated for 15 years, were released.

After the 2023 presidential election, Tshisekedi had a clear lead in his run for a second term. On 31 December 2023, officials said that President Felix Tshisekedi had been re-elected with 73% of the vote. Nine opposition candidates signed a declaration rejecting the election and called for a rerun.

Continued conflicts
The inability of the state and the world's largest United Nations peacekeeping force to provide security throughout the vast country has led to the emergence of up to 120 armed groups by 2018, perhaps the largest number in the world. Armed groups are often accused of being proxies or being supported by regional governments interested in Eastern Congo's vast mineral wealth. Some argue that much of the lack of security by the national army is strategic on the part of the government, who let the army profit from illegal logging and mining operations in return for loyalty. Different rebel groups often target civilians by ethnicity and militias often become oriented around ethnic local militias known as "Mai-Mai".

Tutsi led insurgency
Laurent Nkunda with other soldiers from RCD-Goma who were integrated into the army defected and called themselves the National Congress for the Defence of the People (CNDP). Starting in 2004, CNDP, believed to be backed by Rwanda as a way to tackle the Hutu group Democratic Forces for the Liberation of Rwanda (FDLR), rebelled against the government, claiming to protect the Banyamulenge (Congolese Tutsis). In 2009, after a deal between the DRC and Rwanda, Rwandan troops entered the DRC and arrested Nkunda and were allowed to pursue FDLR militants. The CNDP signed a peace treaty with the government where its soldiers would be integrated into the national army.

In April 2012, the leader of the CNDP, Bosco Ntaganda and troops loyal to him mutinied, claiming a violation of the peace treaty and formed a rebel group, the March 23 Movement (M23), which was believed to be backed by Rwanda. On 20 November 2012, M23 took control of Goma, a provincial capital with a population of one million people. The UN authorized the Force Intervention Brigade (FIB), which was the first UN peacekeeping force with a mandate to neutralize opposition rather than a defensive mandate, and the FIB quickly defeated M23. The FIB was then to fight the FDLR but were hampered by the efforts of the Congolese government, who some believe tolerate the FDLR as a counterweight to Rwandan interests. Since 2017, fighters from M23, most of whom had fled into Uganda and Rwanda (both were believed to have supported them), started crossing back into DRC with the rising crisis over Kabila's extension of his term limit.

After rising insecurity, President Tshisekedi declared a "state of siege" or state of emergency in North Kivu, as well as Ituri province, in the first such declaration since the country's independence. The military and police took over positions from civilian authorities and some saw it as a powerplay since the civilian officials were part of the opposition to the President. A similar declaration was avoided for South Kivu, in a move believed to avoid antagonizing armed groups with ties to regional powers such as Rwanda.

Mai Mai insurgencies
Ethnic conflict in Kivu has often involved the Congolese Tutsis known as Banyamulenge, a cattle herding group of Rwandan origin derided as outsiders, and other ethnic groups who consider themselves indigenous. Additionally, neighboring Burundi and Rwanda, who have a thorny relationship, are accused of being involved, with Rwanda accused of training Burundi rebels who have joined with Mai Mai against the Banyamulenge and the Banyamulenge is accused of harboring the RNC, a Rwandan opposition group supported by Burundi. In June 2017, the group was formed called the National Coalition of the People for the Sovereignty of Congo (CNPSC) or Alliance of Article 64, a reference to Article 64 of the constitution, which says the people have an obligation to fight the efforts of those who seek to take power by force, in reference to President Kabila. It is one of three alliances of various Mai-Mai militias and is led by Bembe warlord William Yakutumba whose Mai-Mai Yakutumba is the largest component of the CNPSC and has had friction with the Congolese Tutsis. was formed and even briefly capturing a few strategic towns. In May 2019, Banyamulenge fighters killed a Banyindu traditional chief, Kawaza Nyakwana. Later in 2019, a coalition of militias from the Bembe, Bafuliru and Banyindu are estimated to have burnt more than 100, mostly Banyamulenge, villages and stole tens of thousands of cattle from the largely cattle-herding Banyamulenge. About 200,000 people fled their homes.

Clashes between Hutu militias and militias of other ethnic groups has also been prominent. In 2012, the Congolese army in its attempt to crush the Rwandan backed and Tutsi-dominated CNDP and M23 rebels, empowered and used Hutu groups such as the FDLR and a Hutu dominated Maï Maï Nyatura as proxies in its fight. The Nyatura and FDLR even arbitrarily executed up to 264 mostly Tembo civilians in 2012. In 2015, the army then launched an offensive against the FDLR militia. The FDLR and Nyatura were accused of killing Nande people and of burning their houses. The Nande-dominate UPDI militia, a Nande militia called Mai-Mai Mazembe and a militia dominated by Nyanga people, the "Nduma Defense of Congo" (NDC), also called Maï-Maï Sheka and led by Gédéon Kyungu Mutanga, are accused of attacking Hutus. In North Kivu, in 2017, an alliance of Mai-Mai groups called the National Movement of Revolutionaries (MNR) began attacks in June 2017 includes Nande Mai-Mai leaders from groups such as Corps du Christ and Mai-Mai Mazembe. Another alliance of Mai-Mai groups is CMC which brings together Hutu militia Nyatura and are active along the border between North Kivu and South Kivu. In September 2019, the army declared it had killed Sylvestre Mudacumura, head of the FDLR, and in November that year the army declared it had killed Juvenal Musabimana, who had led a splinter group of the FDLR.

Allied Democratic Forces insurgency
The Allied Democratic Forces (ADF) has been waging an insurgency in the Democratic Republic of the Congo and is blamed for the Beni massacre in 2016. While the Congolese army maintains that the ADF is an Islamist insurgency, most observers feel that they are only a criminal group interested in gold mining and logging. In March 2021, the United States claimed that the ADF was linked to the Islamic State of Iraq and the Levant as part of the Islamic State's Central Africa Province. By 2021, the ADF was considered the deadliest of the many armed groups in the east of the country.

Conflict in Katanga
In Northern Katanga Province starting in 2013, the Pygmy Batwa people, whom the Luba people often exploit and allegedly enslave, rose up into militias, such as the "Perci" militia, and attacked Luba villages. A Luba militia known as "Elements" or "Elema" attacked back, notably killing at least 30 people in the "Vumilia 1" displaced people camp in April 2015. Since the start of the conflict, hundreds have been killed and tens of thousands have been displaced from their homes. The weapons used in the conflict are often arrows and axes, rather than guns.

Elema also began fighting the government mainly with machetes, bows and arrows in Congo's Haut Katanga and Tanganyika provinces. The government forces fought alongside a tribe known as the Abatembo and targeting civilians of the Luba and the Tabwa tribes who were believed to be sympathetic to the Elema.

Conflict in Kasai
In the Kasaï-Central province, starting in 2016, the largely Luba Kamwina Nsapu militia led by Kamwina Nsapu attacked state institutions. The leader was killed by authorities in August 2016 and the militia reportedly took revenge by attacking civilians. By June 2017, more than 3,300 people had been killed and 20 villages have been completely destroyed, half of them by government troops. The militia has expanded to the neighboring Kasai-Oriental area, Kasaï and Lomami.

The UN discovered dozens of mass graves. There was an ethnic nature to the conflict with the rebels being mostly Luba and Lulua and have selectively killed non-Luba people while the government allied militia, the Bana Mura, constituting people from the Chokwe, Pende, and Tetela, have committed ethnically motivated attacks against the Luba and Lulua.

Conflict in Ituri
The Ituri conflict in the Ituri region of the north-eastern DRC involved fighting between the agriculturalist Lendu and pastoralist Hema ethnic groups, who together made up around 40% of Ituri's population, with other groups including the Ndo-Okebo and the Nyali. During Belgian rule, the Hema were given privileged positions over the Lendu while long time leader Mobutu Sese Seko also favored the Hema. While "Ituri conflict" often refers to the major fighting from 1999 to 2003, fighting has existed before and continues since that time. During the Second Congolese Civil War, Ituri was considered the most violent region. An agricultural and religious group from the Lendu people known as the "Cooperative for the Development of Congo" or CODECO allegedly reemerged as a militia in 2017 and began attacking the Hema as well as the Alur people to control the resources in the region, with the Ndo-Okebo and the Nyali also involved in the violence. After disagreements over negotiating with the government and the killing of CODECO's leader, Ngudjolo Duduko Justin, in March 2020, the group splintered and violence spread into new areas. In late 2020, CODECO briefly held the capital of the province, Bunia, but retreated. In June 2019, attacks by CODECO led to 240 people being killed and more than 300,000 people fleeing.

The Allied Democratic Forces (ADF), mostly active in North and South Kivu has also been involved in Ituri province. President Tshisekedi declared a "state of siege" or state of emergency in the province in May 2021 to tackle ADF. However, ADF killed 57 civilians in one attack in the same month in one of its deadliest single attacks. 30 people were massacred in September 2021 by the ADF. The President is accused of promoting former rebel leaders and generals accused of war crimes to be in charge of the province.

Dongo Conflict
In October 2009 a conflict started in Dongo, Sud-Ubangi District where clashes had broken out over access to fishing ponds.

Yumbi Massacre (2018)
Nearly 900 people were killed between 16 and 17 December 2018 around Yumbi, a few weeks before the Presidential election, when mostly those of the Batende tribe massacred mostly those of the Banunu tribe. About 16,000 fled to neighboring Republic of the Congo. It was alleged that it was a carefully planned massacre, involving elements of the national military.