R2I or resistance to interrogation is a name for a set of techniques taught to UK, and other NATO soldiers ostensibly to help them, after capture by the enemy, to resist interrogation techniques such as humiliation and torture.
The trainees undergo practices such as hooding, sleep deprivation, time disorientation, prolonged nakedness, sexual humiliation and deprivation of warmth, water and food. Many of these techniques are against international law if used in interrogations.
According to The Guardian this training influenced the interrogation of Iraqi detainees by US soldiers at Abu Ghraib prison. These techniques were allegedly taught specifically to US military intelligence officers who later went to Iraq to perform interrogations. The story in The Guardian tells of a correlation between techniques routinely used in RTI and those allegedly used on prisoners at Abu Ghraib, but offers no definitive proof of causation.
Standard RTI for most special military branches of American and European governments covers both tortures that are condemned by the United Nations and interrogation techniques that are considered legitimate, usually presented along a sliding scale. I.e. a soldier would be subjected to slight discomforts before being subjected to more tortuous techniques.
The most intense RTI was supposedly carried out by the Russian special purpose regiment (Spetsnaz) when the Soviet Union was still intact. The training of this regiment (more accurately referred to as a Corps as there were as many as 20,000 members at its peak) was world-renowned, especially in military circles, for its brutality.
RTI is a product of the market for military information, which has been in place since as early as when Sun Tzu wrote The Art of War. Especially moving into modern times, when information and technology is often more important than numbers in combat, and when torture has been used less often to humiliate and more often to exact information, RTI has become a integral part of military training in most Western countries in one way or another.