What is brainwashing?

Brainwashing is a severe form of social influence that causes changes in someone's way of thinking without that person's consent and often against his will. The "brainwasher" - that is, the influencing agent - actively breaks down the target's identity and replaces it with another set of behaviors, attitudes and beliefs that work in the target's current environment. So invasive is the influence that it requires the total isolation and dependency of the subject, which is why the most familiar brainwashing occurs in cults or prison camps.
The agent requires complete control over the target, with sleep patterns, eating, using the bathroom and fulfillment of other basic human needs depending on the agent's will.
Most psychologists believe that brainwashing is possible under the right conditions. Some, however, see it as improbable or at least as a less potent influence than the media portrays it. Many experts believe that even under ideal conditions, the effects of brainwashing are most often short-term. The victim's old identity, they say, is not eradicated but instead is in hiding, and once the "new identity" is no longer reinforced, the person's old attitudes and beliefs begin to return.
During the Korean War, Korean and Chinese captors reportedly brainwashed American prisoners of war. Several POWs ultimately confessed to waging germ warfare -- which they hadn't -- and pledged allegiance to communism by the end of their captivity. About two dozen soldiers (a tiny fraction of the 20,000-plus prisoners in communist countries) refused to come back to the United States when they were set free.
Some psychologists say the apparent conversion of those POWs was the result of plain-old torture, not "brainwashing." And the fact that so few were converted leads to a question of reliability: Is brainwashing a system that produces similar results across cultures and personality types, or does it hinge primarily on a particular target's susceptibility to influence?