Torture, according to the international Convention against Torture (CAT) is as "any act by which severe pain or suffering, whether physical or mental, is intentionally inflicted on a person for such purposes as obtaining from him or a third person information or a confession, punishing him for an act he or a third person has committed or is suspected of having committed, or intimidating or coercing him or a third person, or for any reason based on discrimination of any kind, when such pain or suffering is inflicted by or at the instigation of or with the consent or acquiescence of a public official or other person acting in an official capacity." It does not include pain or suffering arising only from, inherent in or incidental to lawful sanctions. It excludes pain and suffering caused by lawful sanctions, such as corporal or capital punishment. It does, however, broaden the classic definition of physical harm to include intimidation. For the purposes of this article, torture is specifically a function of a government or quasi-state, rather than the actions of an individual who inflicts pain for personal reasons such as revenge or sadism; this differentiate reflects the CAT, Geneva Conventions, and the position of the World Medical Association.
Under the CAT, if capital punishment were ordered through a legal process, it would not qualify as torture, but as pain and suffering incidental to a judicial sanction. The concept of "cruel and unusual punishment", while not limited to the Eighth Amendment to the United States Constitution, is by no means universal. While there was much outcry when Singapore ordered caning as part of a judicial sentence, there was no major outcry that it violated international law.
Many medieval and ancient acts were not, in this sense, meant as torture, but as painful methods of execution. There certainly were medieval tortures, however, not intended to be lethal, but have fallen into disuse in favor of means that are simpler or more "scientific". In the current context, the emphasis is not on the deliberate killing of a prisoner by painful means; see capital punishment.
Motivations for torture
Why do governments and quasi-states torture? Darius Rejali, a political science professor and specialist in the area, proposed three main purposes in a 2007 book:
- General intimidation
- Coercion of confessions desired for political reasons, where the truth or falsehood of the confession is less important than its existence
- Collection of accurate information
To answer the question "does terror work?", he poses eight questions, the first four of which apply to all of the reasons above, while the last applies only to information gathering: 
1. Can torture be scientific?
2. Can one produce pain in a controlled manner?
3. Does technology help torturers in this respect?
4. Can pain be administered respectfully and professionally?
5. Can interrogators separate deceptive from accurate information when it is given to them?
6. How accurately to co-operative prisoner remember information after torture?
7. Does this investigative method yield better results than others normally at an army's disposal?
8. If not, does this investigative method yield better results under conditions of constrained time? [i.e., the "ticking bomb scenario"]
Several factors limit the utility of torturing an individual, depending on the intention:
- Death or permanent uncommunicative states
- Unconsciousness or inability to speak
- Visible physical damage
- Physical and psychological damage to individuals intended to return to society
These are broader factors, however, than the efficacy of torture in achieving results with an individual. It can have adverse effects on the torturer's cause. The use of torture by the French in Algeria, may have allowed the FLN (Front de Libération Nationale) to win, even though the FLN itself practiced terrorism and torture. French methods prevented natives opposed to the FLN from seeking French protection.
Purpose of torture
The basic definition of torture is that it causes pain. While it is widely accepted that psychological pain is real, the matter becomes much more blurred when the effect of a procedure, such as sensory deprivation, is to disorient rather than explicitly distress.
Pain alone, from the examples of religious martyrs, is not always sufficient to produce a desired change in behavior. Certainly not in religious contexts alone, many have found truth in Nietzsche's observation "that which does not destroy us makes us the stronger."
The "KUBARK Counterintelligence Interrogation" manual (KUBARK is a cryptonym for the CIA) observed "If an interrogatee is caused to suffer pain rather late in the interrogation process and after other tactics have failed, he is almost certain to conclude the interrogator is becoming desperate. He may then decide that if he can just hold out against this final assault, he will win the struggle and his freedom."
Certainly in some contexts, torture may more reinforce the self-image of the torturer than achieve the ostensibly desired effect. In other, not mutually exclusive contexts, the torturer himself may be damaged by what he does; this was notable in the Great Terror in the Soviet Union from 1934-1939 when Joseph Stalin ruthlessly repressed political opposition.
Intimidation and generic countersubversion
Many governments have at times used torture, or the fear of it, as part of a broader program to suppress dissent. During the Algerian War of 1954-1962, the counterinsurgency advisor, Roger Trinquier, wrote, in his book, Modern Warfare, that defeating an insurgency requires the unconditional support of the populace, which must be maintained at any price, including terrorizing them. This view, that it is more important to be feared than admired, is one with which many other counterinsurgency theorists disagree, preferring the population see legitimacy and value in government. "An unceasing watch is exercised over all the inhabitants. Any suspicion or indication of lack of submission is punishable by death, quite often preceded by horrible torture."  Trinquier was one of the theorists that believed that terrorists would be deterred by even more intense terror directed at them.
Intimidation was also an important part of Latin American control, during the "dirty wars". Some of this was indigenous; some was influenced by diffusion from the U.S.A. In Argentina, there is no law regulating the powers or providing for accountability and control over the activities of the intelligence agencies, which, with the military and police, practiced "state terror. During the years of dictatorship, the main role of the Armed Forces in Argentina shifted form defending the country from external aggressions to defending it from its internal enemies."
In 1975, an Argentinian military coup established a government that widely used torture to suppress dissent.
Until the 1976 coup, and for months afterwards, the U.S.A. relied to a large extent on the armed forces as its main interlocutors in Argentina's turbulent politics. Unlike in Chile and Uruguay, where the U.S had backed reformist parties (at least until the emergence of a serious left-wing challenge in the early 1970s), it was consistently hostile to the most popular political movement in Argentina, Peronism. In the face of Juan Peron's populist rhetoric, economic nationalism, and fascist sympathies, the military seemed to provide a moderate alternative, favorable to American investment, and just as staunchly anti-communist.
According to Senator Alan Cranston, Congress, in 1974, banned police training, after learning of training and equipping "police in Iran, Vietnam, Brazil, and other countries were involved in torture, murder, and the suppression of legitimate political activity":
- training was provided to so-called friendly anti-Communist regimes, without regard to whether they were dictatorships or not.
- law enforcement efforts were subordinated to U.S. counterinsurgency goals. ...U.S. training included such topics as counterinsurgency techniques, weapons use, and Communist ideology. This also meant, in practice, reinforcing the control of recipient countries' militaries over the police.
Other Latin American countries, especially Honduras, drew from Argentina as much or more as from the U.S.A. In June 1983, the non-governmental organization (NGO) Americas Watch wrote "General Gustavo Alvarez Martínez, head of the Hondurian military staff, has publicly defended the use of the Argentine method to confront the subversive threat in Latin America. As a matter of fact, Alvarez is responsible of having brought to Honduras the first Argentine military instructors, when he was commandant of the Fuerza de Seguridad Pública (FUSEP [Public Security Force]).
- See also: Thought reform
How is it possible that a person confesses to crimes which he has not committed? Only in one way — because of applications of physical methods of pressuring him, tortures, bringing him to a state of unconsciousness, depriving him of his judgment, taking away his human dignity. In this manner were "confessions" obtained. — Nikita Khruschev, (1894-1971) speaking of the Great Terror
During the Great Terror, a distinction was made between "informal" torture, such as beatings, and officially authorized torture. It was only in 1937, at the Zinoviev Trial, where authorization had been given by a order from Stalin, not widely disseminated until 1939. The British historian Robert Conquest observes that Stalin was a great believer in terror, but "torture is not a complete explanation when it comes to the public confessions of the oppositionists...But critics were right in saying torture alone could not have produced the public self-humiliation of a whole series of Stalin's enemies, when returned to health and given a platform. We shall see, in fact, that some accused withdrew in closed court confessions obtained by torture. 
Conventional opinion generally suggests that torture is rarely effective in obtaining reliable strategic (i.e., long-term) information, although it certainly can have a role in the coercion of confessions for legal or propaganda purposes. Its value for obtaining specific tactical "ticking-bomb" information is much more controversial, as is the existence of the "ticking-bomb scenario": only one specific piece of information is needed.
Some legal experts, such as Alan Dershowitz, have suggested court supervision of "torture warrants" for true ticking bomb matters. Others, such as John McCain, have suggested they stay criminalized, but that a jury may determine that the torturer had justification. There is no consensus, although interrogation specialists tend to be dubious on the value of torture in tactical situations. It does seem to have been a Soviet Spetsnaz technique.
Trinquier believed torture could be used to collect information, as well as intimidate.
If the prisoner gives the information requested, the examination is quickly terminated; if not, specialists must force his secret from him. then, as a soldier, he must face the suffering, and perhaps the death, he has heretofore managed to avoid.
Various police and intelligence experts have observed a phenomenon of "de-skilling". Overdependence on torture and an emphasis on confessions do not encourage eduction of reliable information or evidence that is untainted in court proceedings.
Controlling the application of torture
While various governments have imposed regulations on the allowable extent of torture, sometimes as an exercise and sometimes quite seriously, there often are no guarantees on whether the torturers will follow them. This is an especially important distinction when different people interrogate and "soften up" for interrogation. While interrogators, with intelligence or police investigative training, often have a sense of psychological and physical limits, guards and pure torturers may not.
Some torturers get emotional gratification from a sense of personal power, or sadism that qualifies as paraphiliac. Others may act from hatred. Within communities of torturers, there may be a competitive impetus, based on novelty and intensity rather than results.
Legal and ethical concerns
Prohibition against torture and other degrading punishments is part of many articles of international law. Article 5 of the Universal Declaration of Human Rights 1948  and Article 3 of the European Convention for the Protection of Human Rights and Fundamental Freedoms 1950  prohibit the use of torture. These have evolved into the Convention against Torture.
Many religious bodies have explicitly denounced torture. In the U.S.A., the National Religious Campaign Against Torture counts as members a variety of denominations including many Unitarians, Presbyterians, Catholics, Methodists and others. Humanists generally oppose torture.
The World Medical Association has declared its opposition to torture,  and the American Medical Association have passed resolutions banning their members from participating in torture, although they may provide medical care to those being tortured. The American Psychological Association has passed a resolution that bans psychologists from participating in some of the stronger interrogation techniques that border on torture.
National security concerns
There is considerable current argument if some coercive interrogation techniques, perhaps in a gray area of being torture or not, are justified by military necessity. This is an especially challenging issues in dealing with non-national terrorism, where there are limited sources of intelligence and prisoners may be highly motivated to resist other interrogation methods. Constitutional and defense attorney Alan Dershowitz, for example, said  described "the worst of all worlds" as "I think torture will be used -- and has, in fact, been used -- whenever it is felt that by torturing an obviously guilty [terrorism suspect], the lives of multiple innocent people could be saved,...The problem is that today, torture is being used promiscuously, and we deny we're using it." He said the use of torture should be a Presidential-level decision, with the issuance of torture warrants. "He ought to have to sign a torture warrant in which he says, 'I'm taking responsibility for breaking the law, for violating treaties, for doing an extraordinary act of necessity.' That's a responsibility only the president should be able to take, and only in the most extraordinary situation."
A counterargument is that in a war of ideas and ideologies, the use of torture may have side effects worse than the information gained. In the context of disclosures of methods used during the George W. Bush Administration, Dennis Blair, the current U.S. Director of National Intelligence, said "The information gained from these techniques was valuable in some instances, but there is no way of knowing whether the same information could have been obtained through other means. The bottom line is these techniques have hurt our image around the world, the damage they have done to our interests far outweighed whatever benefit they gave us and they are not essential to our national security." This has been called a political argument by former Bush Administration officials, especially Vice President Dick Cheney.
This is not, however, a U.S. argument alone; see the discussion above of whether France lost Algeria, in part, due to the use of torture. 
Diffusion of torture techniques
Rejali, in 1998, introduced the idea that torture technologies diffuse across time and space, to different organizations using those technologies. He selected electrical methods to test the model, as a problem in the sociology of technology, because the methods and their variants are clearly identifiable, and the origin of general electrical technology is recent enough to map torture techniques that evolved from it.  The idea of diffusion of torture techniques, however, is more general than studying the use of electrical methods. It can, for example, throw light on the practices of particular torturing organizations, and where they learned their methods. When a country that liberally engaged in torture, but did not use methods that originated with a country that trained them in interrogation, it is reasonable to assume that the first country has an indigenous tradition of torture.
In his 2007 work, he speaks of indication of deliberate diffusion when "independent reports on the ground confirm the presence of a signature technique or procedure for another nation with whom the police had contact."  The presence of foreign advisers has to map to the pattern of torture. He cites the first observations, in Chilean torture beginning in 1973, of a Brazilian signature technique called the pau de arata ("Parrot's Perch"), a combination of positional and electrical torture. He questions the claims of some groups that the mere presence of military or police advisers is adequate to document government-to-government transfer. Brazil was known to have conducted classes for other Latin American countries. 
It has been reported that an American trainer, Dan Mitrione (who was later killed by Uruguyan insurgents) taught torture techniques, but it is possible that he did so on his own initiative.  However, the American historian William Blum assumes that this was a matter of policy.  although he agrees that Uruguayan police tortured prisoners before there were any U.S. advisers. He quotes the former Uruguayan Chief of Police Intelligence, Alejandro Otero, as saying "US advisers, and in particular Mitrione, had instituted torture as a more routine measure; to the means of inflicting pain they had added scientific refinement; and to that a psychology to create despair, such as playing a tape in the next room of women and children screaming and telling the prisoners that it was his family being tortured."
Variability of torture techniques
Torture, however, rarely is standardized, especially after diffusion through years and translations. It is relatively rare to find formal training in torture, but even more rare to discover specific linkages between torture and interrogation. Brazil conducted actual classes in the 1960s. 
There often is no actual doctrine. There is little question that SERE techniques, taught to U.S. aircrew and special operators who might become prisoners, diffused to Guantanamo detention camp and then to Iraq, according to a sworn statement by the former chief of the Interrogation Control Element at Guantánamo said "When I arrived at GTMO,my predecessor arranged for SERE instructors to teach their techniques to the interrogators at GTMO ... The instructors did give some briefings to the Joint Interrogation Group interrogators."  SERE techniques are indeed drawn from real-world experience of Americans in Korean and Vietnamese prison camps. The torturers at those camps, however, were intent on obtaining confessions for propaganda purposes, not in educing reliable information.  While there are reports that CIA psychologists, with SERE experience, did advise the Army interrogation programs, there is little in the intelligence literature to suggest that techniques useful for coercing confessions are useful for producing accurate information.
There does seem to have been informal diffusion. It may be argued if the use of military working dogs, to intimidate prisoners known to be frightened by them, constitutes torture, testimony indicates that while dogs were used for intimidation at Guantanamo detention camp, and the techniques taught to guards at Abu Ghraib prison, there seemed no concept of how they would be used in relation to interrogation, other than intimidating prisoners before interviews.  The personnel given the dog training in Iraq were military police, not intelligence interrogators, in violation of U.S. regulations that military police should not be used for preparing prisoners for interrogation — although those regulations were sometimes waived in the George W. Bush Administration. There ware also cases of abuse at Abu Ghraib that had no clear relationship to interrogation requests, but seemed simple dominance or sadism.
Rejali points to various U.S. military training programs for training intelligence personnel of foreign countries, mentioning that programs from 145 to 177 hours long contained only relatively short sections on prisoner handling, usually combined with document analysis. Actual interrogation training in these courses could be as little as one hour. It should be emphasized this was "interrogation" training and might or might not have included torture. He concludes that torturers probably do not learn their craft from formal national training programs interrogation. He suggests that the techniques might be learned indirectly from resistance to torture programs such as R2I and SERE. He suggests that the most common method is informal transmission among soldiers and police, and that there is little direct communication between intelligence professionals and those who would be most likely to torture. 
Techniques may change when the goals change. He observes that South African practice changed from forced standing to electrical torture, when the police became more interested in extracting information than coercing confessions.
Resistance to torture
Another indication of how nations regard torture is how military forces train their personnel to resist acts expected if captured by enemies. During the Second World War, there was training on how to resist interrogation, especially for personnel assigned to secret operations. In such cases, the goal was for them to resist until their comrades would detect their absence and disperse. The OSS, among other organizations, taught the use of cover stories, but they also gave their agents "L-pills", or quick-acting poison to give them a choice of suicide rather than facing torture.  In contrast, the Japanese assumed their troops would never be captured alive, so ignored resistance training. Japanese soldiers, for example, who had been captured while unconscious, felt they were dead to their own society due to the disgrace of capture, and often actively cooperated with what they saw as their new society.
More formal resistance training began after the experiences of "brainwashing" in the Korean War. The U.K. began at its Joint Services Intelligence School at Maresfield, where the course is now called or "resistance to interrogation" (R2I)  The U.S. equivalent is called SERE: survival, evasion, resistance and escape.
Diffusion of the resistance techniques has been observed, as well as explicit training of interrogators by the resistance instructors. For example, resistance to positional torture, taught in R2I were later observed in use by the Royal Ulster Constabulary in Northern Ireland. British sources report the use of R2I techniques at Abu Ghraib; the observation was made that the knowledge was used very differently by special operations forces who themselves might be subjected to torture, and by interrogators who would not be in danger. "...frontline soldiers who are made to experience R2I techniques themselves develop empathy. They realise the suffering they are causing". 
Actions that leave scars or other permanent injury clearly qualify as torture. When the goal is intimidation of the subject or a group, visible damage indeed may be a goal. Most modern definitions include techniques that do not do substantial damage, but convince the subject that there is a serious danger of permanent injury or death. The term "clean torture" is sometimes used for forms that do not leave obvious marks. Sophisticated medical examinations can sometimes reveal evidence of "clean" torture. 
A blurred area, however, has been called "sweating" in Western practice, or "the Conveyor" in Soviet parlance.  Some documents, such as KUBARK, distinguish these as "coercive interrogation", but not torture, as they are extremely unpleasant but do not meet the criterion of fear of death or disability.
A range of coercive interrogation techniques, used worldwide by police organizations, are at the edge of many definitions of torture, characterized by relays of interrogators, conducting the interviews in poorly ventilated, hot rooms, often with blinding lights in the subject's eyes. Not all interrogation techniques, however, are physically damaging, psychologically stressful, or even coercive.
The heat and light may continue when the subject is not being interviewed, causing sleep deprivation. They may extend to positional and exhaustion methods and to "clean" beating. This set, combined with psychological pressure, characterized both Soviet and Asian communist methods,  but were certainly seen with Western police "third degree" methods, such as those described by the U.S. Wickersham Commission in 1931.
Psychological pressures can be divided into those directed against the subject, and those directed at persons valued by the subject.
A basic approach to psychological interrogation, which is probably licit at one end and torture at the other end of the spectrum, involves disorientation. Methods can include preventing sleep, sensory deprivation, exposure to extreme sensory stimuli, etc.
Psychological interrogation can be effective without involving terror. Some guidelines for interrogators include being correct and maintaining a position of authority, without being cruel. There are reports of interrogators, working in the Middle East, who can disorient a prisoner who is expecting torture by formally serving him coffee or tea, perhaps bread and salt in the guest ritual, and then courteously but relentlessly asking questions.
A sense of omniscience is critical in psychological interrogation, which often comes from analysts listening to recordings of every interrogation, then searching through data bases to find correlations, true names, etc., with which the prisoner can be confronted. See Intelligence analysis management. 
On the other extreme, however, simulated executions, in which the subject is tied to a post, orders given to a firing squad, but blank ammunition fired, qualifies as psychological torture to most observers.
While South Vietnamese interrogators used physical torture against Nguyen Thi, one assessment is that the most important information gained was from principally psychological methods.
While the South Vietnamese use of torture did result (eventually) in Tai's admission of his true identity, it did not provide any other usable information. The South Vietnamese played the key role in cracking Tai's cover story, but it was their investigation and analysis that put the pieces together to make a solid and incontrovertible identification of Tai, not their use of torture, that scored this success. A sensitive, adept line of questioning that confronted Tai with this evidence and offered him a deal--like the offer by his torturers to exchange admission of his identity for consideration in a notional prisoner exchange--would almost certainly have achieved the same result. Without doubt, the South Vietnamese torture gave Tai the incentive for the limited cooperation he gave to his American interrogators, but it was the skillful questions and psychological ploys of the Americans, and not any physical infliction of pain, that produced the only useful (albeit limited) information that Tai ever provided.
While withdrawal from external stimuli has been practiced as an aid to meditation throughout history, the ability to meditate deeply is a learned skill. Beginning in the early 1950s, the effect of sensory isolation was studied for a variety of purposes. Some of the first work came from Donald Hebb, some of whose work was funded by the Canadian Defense Research Board to explore the problems of false sensation by people in monotonous jobs, such as driving trucks or monitoring radar screens. Hebb later stated, in John Lilly's book, that while the stated purpose was true, it was also done in pursuit of methods for brainwashing. His experiment allowed the subject to stop at any time, but did explore the role of perception as it might relate to Korean activities.  John Lilly, who also worked in this area, disagreed with the term "deprivation", saying .."'sensory deprivation' was invented by those psychologists who did not do self-investigation and who did experiments on subjects, expecting a "deprivation state" in the isolated circumstances. In a series of over three hundred subjects we have found no such states of 'deprivation,' nor the predicated 'stress' of physical isolation."
Just as some subjects are disoriented without sensory cues, others become disoriented when their senses are overloaded. Lights, beyond the glare in the eyes of "sweating", can be kept on continuously, or the victim can be exposed to intense flashes of light. Sound can take the form of extremely loud music, white noise, or feedback of one's own heartbeat or screams. Loud music can also have content highly offensive to certain cultures.
Among the greatest supports to an individual under stress, as in a prison camp, is from a peer group. Encouraging rejection, therefore, aggravates the stress of individual psychological torture. Zimbardo found group pressure against a nonconforming individual, even in the context of a simulated prison experiment, to be extremely distressing in a very brief time. 
Another technique of psychological torture is the threat, or actual physical torture, of loved ones. "The psychological effects of having to witness the torture of a family member or having to endure sexual forms of ill-treatment may be as traumatic as maiming – or worse."
Some groups have used systematic sexual abuse of groups as a means of large-scale intimidation, as in Kosovo.  Such actions can have especially catastrophic effects in societies where the fact of rape, regardless of guilt, may be perceived as damaging family honor, even necessitating honor killing.
Positional torture involves putting the victim, with or without restraints, in a position that becomes painful when prolonged. Some positions, such as kneeling on small hard objects, are immediately painful, but even standing, without the opportunity to change posture, can become extremely uncomfortable. Something as apparently neutral as standing can have physiological effects, such as edema from the gravitational pooling of fluid. Donald Rumsfeld, the U.S. Secretary of Defense who appears to have authorized coercive interrogation methods that may have gone over the line into torture, wrote "I stand for 8-10 hours a day. Why is standing limited to 4 hours?"  Rumsfeld, who uses a stand-up writing desk, however, was free to shift position. In fairness, at the time quoted, he refused permission for some techniques and said others were permissible only with his personal, case-by-case, advance approval.
"Clean beating" does not leave obvious injuries. Typically, they are inflicted with hands, or objects, such as rubber hoses or sandbags, without sharp edges. They tended to be to softer parts of the body less likely to bruise. Particularly when thorough medical examination is done soon after the act, even though there may be no visible marks, it may be possible to detect evidence of muscle damage with laboratory determinations of urine myoglobin.  After longer periods, sophisticated imaging methods may reveal patterns of damage, even when there has been time for healing. There may be, for example, patterns of healed fractures, or detectable scar tissue.
The classical methods include whipping and beating, abnormal stretching of joints, burning, and cutting. Obviously, these usually have a significant probability of permanent damage. Many classic tortures of the Inquisition, such as the rack on which a person's body was pulled beyond the normal limits, were of this type. Damaging methods continue to exist, such as strappado or other methods by which a person is suspended so that his weight dislocates joints, thumbscrews or other devices to crush body structures, or burns inflicted with heat, electricity or chemicals. Unquestionably, the Gestapo and other Nazi security organizations used damaging methods, but there was no standardization among Gestapo offices. Damaging acts were more common in occupied France than in Germany, outside concentration camps. Martin Sommer, a Gestapo official at Auschwitz, often killed his prisoners after torture. .
During the Great Terror, Soviet interrogators would use damaging torture on prisoners not destined for show trials.
Water has been used as the basis for many forms of torture, ranging from often-fatal forcing of water down a funnel or tube in the throat, to submersion, to simulated drowning with the method of waterboarding. The latter, and related methods involve oxygen deprivation without introducing water into the victim's body. Water methods may be made more painful with the addition of irritating chemicals to the liquid. Choking, by total immersion in water, is perhaps the oldest version, with "ducking" prescribed by the Code of Oleron, instituted in the 12th century, for misbehavior by sailors.  Submersion in an icy bathtub was a signature of the Gestapo in France.
Modern references differentiate between techniques that deprive air but do not use water, often called "dry submarine" methods, and submersion called "wet submarines".  Dry submarines may not use water, but only a clinging and suffocating material such as a plastic bag, as in Venezuela in 1970. 
Waterboarding interrogation techniques may be a "dry submarine" asphyxiation method, if water is poured to give the reflexive sense of drowning, but not actually allowed it to enter the victim and cause additional metabolic disturbances. If, however, the water is poured over a rag or other material in the victim's mouth, it becomes closer to the "Dutch method" of choking. The earliest form of this used a rag stuffed into the victim's mouth. While this could cause intense pain, it was less likely to cause organ damage than pumping. Water flowing over the face, however, itself triggered a drowning reflex and extreme terror, perhaps even more so than the deadlier pumping with a hose or funnel. It is this flow-across-face aspect that seems a key aspect of waterboarding.
Forced swallowing methods, generically called "pumping", distend organs and can easily cause permanent damage.  It was a medieval technique of the Inquisition, used by the United States in the Spanish-American War, was a common technique of the Japanese Kempetai in the Second World War and was a preferred method of the French in the Algerian War. In the Vietnam War, South Vietnamese interrogators, and sometimes Americans, used pumping. 
Other methods intend to cause oxygen deprivation, which triggers reflexive fear and panic. Some involve no water, like the method called the "dry submarine," described by Amnesty International as in use in Venezuela in 1970  or in the Philippines in 2003, 
In the context of U.S. interrogation of suspected terrorists in the George W. Bush Administration, authorized on a case-by-case basis by senior U.S. government officials, waterboarding interrogation techniques, has been described in several ways. One appears to used cellophane or plastic over the face, with water poured over it, so it actually may not admit water to the body. It does induce fear of death both from triggering drowning reflexes caused by water flow, and asphyxiation reflexes caused by the plastic. One could call it a simulated drive of a dry submarine.
Other reports of waterboarding, however, do mention it admitting water to the body as in the Dutch technique. A Navy SERE instructor, Malcolm Wrightson Nance, specifically mentioned this in testimony to the U.S. House of Representatives. 
Electrical torture instruments are of several types. One causes pain and convulsions to the entire body, or large parts of it. Another delivers a painful shock to specific points of the body. A third category is taken from medical electroconvulsive therapy (ECT), which may be used as a technique to intimidate subjects who fear memory loss or to induce forgetting of the torture. ECT, when done without the anesthesia and muscle relaxants standard in regular medical use, also can induce painful convulsions.
An early electrical torture implement, called the picana electrica, was based on a cattle prod, and was first observed in Argentina in 1934. The torture implement requires at least two operators, one to apply the electrical contact to sensitive parts of the victim, who is made wet to improve electrical contact, and then restrained on a table. A second operator controls the shock generator, and a physician may be present to monitor health.
The picana device, however, did not diffuse for next 30 years, when it was seen in Uruguay, Paraguay, and Bolivia. Chilean police, who used other electrical devices, did not use it in the 1970s. Whole-body electrical torture appears to have originated in France, diffused into French Indochina, been adopted by German collaborators in France, to Algeria and then back to Indochina. In Southeast Asia, it was adopted by South Vietnamese and Americans, and was used during the Vietnam War. British colonial use was most prevalent in Kenya, was combined with scarring torture, sometimes in public. French use, however, was much longer term, and focused on not leaving marks.
In 1968, U.S. troops in the Vietnam War were under orders to report all war crimes, specifically including torture, whether by enemy or friendly troops. Previously, they had only been required to report enemy actions, so the use of torture came under much greater scrutiny. This was an impetus to the use of "clean" electrical torture, often administered using a hand-cranked generator on a prisoner, often immersed in water; this was reported by LTC Anthony Herbert in the 1968-1969 period.  Herbert's allegations, described in his book, Soldier, were disputed by Army Criminal Investigation Division.
These measures were carried out by both South Vietnamese and American troops.  U.S. psychiatrists, in 1966, were involved in experiments first using electroconvulsive therapy machines with food withholding, and then the implantation of brain electrodes in 1968. Neither was successful in obtaining information or breaking resistance. 
There have been uses of drugs on nonconsenting subjects, but not all met the definition of torture: the deliberate infliction of suffering. Attempts to use drugs as "truth serums", even those that led to death, as with Frank Olson, violated all standards of medical ethics, but were not torture. While there certainly was much CIA experimentation with drugs, in the 1950s and 1960s, as aids to interrogation, they did not diffuse into the manuals made available in South America. 
When a drug was used, however, as an "agent of punishment", it does qualify as torture. This practice appears to have been most widespread in the Soviet system, which had had an earlier concept of political psychiatry. The use of drugs as punishment appears to have begun in 1960. Some quite legitimate drugs, such as haloperidol, were used in dosages intended to produce confusion, restlessness, and extrapyramidal symptoms.  Others, which induced fever and pain, were used to convince prisoners not to tell "others about his fate".
- United Nations General Assembly (10 December 1984), Convention against Torture and Other Cruel, Inhuman or Degrading Treatment or Punishment, A/RES/39/46
- Steven H. Miles (2006), Oath Betrayed: Torture, Medical Complicity and the War on Terror, Random House, ISBN 1-4000-6578-x, p. 5
- World Medical Association (October 1975 (editorially revised 2006)), Guidelines for Physicians Concerning Torture and other Cruel, Inhuman or Degrading Treatment or Punishment in Relation to Detention and Imprisonment, Declaration of Tokyo
- Darius M. Rejali (2007), Torture and Democracy, Princeton University Press, ISBN 0691114226, p. 23
- Rejali 2007, pp. 446-447
- Daniel Moran (December 2008), "Two Sides of the Same COIN: Torture and Terror in the Algerian War, 1954-62", Strategic Insights
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