The researchers asked a total of 104 men to undergo a variety of procedures to test their pain tolerance, like putting their arms in hot water. All of the men had been Israeli soldiers in combat during the 1973 Arab-Israeli War (the Yom Kippur War), and 60 had been severely tortured as prisoners of war held in Egypt or Syria. Compared to the men who had fought in the war but not experienced torture, the former POWs reported more intense and prolonged feelings of chronic pain. They also showed greater levels of wind-up pain—when an identical painful stimulus repeated multiple times increases the intensity of the pain—and diminished levels of pain inhibition, which is when the body, confronted with two different pain stimuli, lessens one of the two sensations of pain.