National debate about torture continues, but the valuable Vietnam prisoners of war resource goes largely untapped. Most of the POWs held five years or longer were tortured. The Pentagon has never studied our "torture database."

I and many POWs were tortured severely — some to death. Several wrote books. John "Mike" McGrath's book "Prisoner of War: Six Years in Hanoi" includes vivid torture drawings.

In my recent book, "Surviving Hell: A POW's Journey," my editors recommended that I include torture; otherwise younger readers might perceive treatment of detainees at Abu Ghraib and Guantanamo as real torture. There was abuse and humiliation; in Vietnam there was torture.

It's likely we Vietnam POWs would disagree on one definition of torture. Sen. John McCain, George "Bud" Day and I were recently together. Bud, one of the toughest and most tortured POWs, received the Medal of Honor for his heroism as a POW. John thinks waterboarding is torture; Bud and I believe it is harsh treatment, but not torture. Other POWs would have varying opinions.

As one who has been severely tortured over an extended time, my firsthand view is that torture, when used by an expert, can produce useful, truthful information. During torture there is a narrow window-of-truth as pain (often multiple kinds) is increased. If torture continues beyond that point, the person breaks, or dies if he continues resisting.

Each person has a different physical and mental pain threshold. A trained interrogator can identify the exact moment when, if slightly more pain is inflicted, a person can no longer hold out by merely providing name, rank, serial number and date of birth pursuant to the Geneva Convention. At that precise point, the window-of-truth exists, and a person may give useful or truthful information to stop the pain. As slightly more pain is applied, the person loses it. He will say anything he thinks will stop the torture — any lie, story or random words.

This torture window-of-truth is theory to some; it is fact to me. During torture, I had the sickening feeling deep within my soul that maybe I would tell the truth. It is unpleasant, but I can still dredge up the memory of that window-of-truth feeling as the pain intensified.

Our world is not completely good or evil. To proclaim we will never use any form of enhanced interrogation suggests we are naive, and eases our enemies' recruitment of radical terrorists to plot attacks on innocent children, men and women or any infidel. We do not impress radical terrorists like those who slit the throat of Daniel Pearl in 2002 simply because he was Jewish and webcast his dying.

To help define how to obtain information, the Pentagon should tap the Vietnam POW database. They would learn that we developed our own standard and alerted newly captured POWs: "When you can't hold out by simply giving your name, rank, serial number and date of birth, take physical torture until you are right at the edge of losing your ability to be rational. At that point, lie, do, or say whatever you must do to survive. But you first must take physical torture to your limit."

Does use of enhanced interrogation bode badly for future American POWs? Not until all nations and all terrorists sign a treaty and abide by the U.S. Army Field Manual — no threats, no raised voice, no physical torture, no nothing. Until then, we are dreaming to think that our do-nothing interrogation policy will protect captured Americans.

Meanwhile, to define torture and formulate the best policies for productive interrogations, I encourage the Pentagon to tap the rich Vietnam POW database.

Medal of Honor recipient Leo Thorsness is a retired Air Force colonel and author of "Surviving Hell: A POW's Journey."