On each occasion waterboarding has elicited valuable information that has saved lives.
According to evidence given to Congress, water-boarding has been applied to three prisoners since 2002, with the approval of the U.S. attorney-general, and on each occasion the result has been valuable information that has saved lives.
Although the technique is widely regarded as physical torture, and not psychological pressure, most NATO personnel who have undergone escape and evasion training have experienced water-boarding, which is intended to give the impression to the victim that he is in imminent danger of death by drowning.
In fact, of course, there is no such risk, and the application is regarded as a very last resort, after other ruses, such as dummy executions where a victim listens to what appears to be a condemned man is dragged before a firing-squad and shot.
Having been tortured in North Vietnam John McCain has already condemned water-boarding, but his critics point out that al-Quaida does not conform to any internationally-recognised norms of behaviour, and his gesture will certainly not be reciprocated by an adversary that takes advantage of its ability to engage regular combat troops but then seek refuge within the protection of the civilian population.
All hostile interrogations are coercive, as any police officer can testify, but intelligence agencies need to be able to take advantage of prisoners who are at their most vulnerable during the first two or three days after their capture, when they are isolated and have little idea of how long their incarceration might last and often are keen to ingratiate themselves the their interrogator.
In these circumstances prisoners are quite capable of compromising valuable information, and future exploitation of this source should not be denied to the allies.