SENIOR U.S. COMMANDERS in Iraq insist that they never approved harsh interrogation techniques for Iraqi prisoners. Yet those same commanders now acknowledge that abusive practices were employed against detainees all over Iraq -- not just at Abu Ghraib prison -- and in Afghanistan. The International Red Cross has reported scores of incidents, and Gen. John P. Abizaid, the head of U.S. Central Command, said in a Senate hearing yesterday that 75 abuse cases have been investigated, as well as a number of deaths. Some of the methods that the commanders say were never sanctioned in Iraq -- and that, most experts believe, violate the Geneva Conventions -- were nevertheless listed on a sign posted at Abu Ghraib under the heading "Interrogation Rules of Engagement."

How could this massive breakdown of order and discipline have occurred? The Bush administration still tries to blame a few low-ranking reservists who served at Abu Ghraib. But a more convincing answer can be found in a memo submitted to President Bush by White House counsel Alberto R. Gonzales in January 2002. In the memo, which was first disclosed by Newsweek magazine, Mr. Gonzales explained why he believed Mr. Bush should ignore State Department objections to his decision to exclude Afghanistan detainees from the Geneva Conventions. The presidential counsel derided the conventions as "quaint" and "obsolete" and claimed that setting them aside would, among other things, make it harder for prosecutors to charge Americans under U.S. law for alleged crimes against prisoners -- something he presented as a "positive." Such contempt for the rule of law pervaded his argument -- and was endorsed by Mr. Bush.

Mr. Gonzales did, however, point out several risks. Among them, he said, was the danger that "a determination that [Geneva] does not apply to al Qaeda and the Taliban could undermine U.S. military culture which emphasizes maintaining the highest standards of conduct in combat, and could introduce an element of uncertainty in the status of adversaries."

As Senate Armed Services Committee hearings have made clear, that is exactly what happened. Harsh techniques for interrogating prisoners at Guantanamo Bay, Cuba, were developed justified on the grounds that the Geneva Conventions did not apply. These techniques then were used by CIA and Army intelligence teams in Afghanistan and, later, Iraq -- even though Mr. Bush declared that the Geneva Conventions would apply to the Iraq war.

An Army legal adviser working in the Iraqi theater, Col. Marc Warren, described it this way before the Senate Armed Services Committee yesterday: "We, as a task force, did not have" an interrogation policy. "We had other units . . . which had served in Afghanistan, bring in their own policies that had been used in other theaters. Additionally, we had what we call the common law of interrogation approaches . . . which were variations on the authorized approaches." Mr. Warren said that in an attempt to draft a formal policy, Central Command circulated drafts with lists of these procedures, including some from Guantanamo Bay and many of the abusive ones later posted at Abu Ghraib. They were not included in the eventual policy -- but it was too late.

Until the Bush administration took office, the U.S. Army operated according to the Geneva Conventions as spelled out in its manuals. But in the chaos of Iraq, there was no firm policy; for U.S. soldiers on the ground, there was "an element of uncertainty in the status of adversaries," as Mr. Gonzales foresaw. And so interrogation methods that the administration had approved for the Taliban and al Qaeda filtered into the theater, in part through intelligence units and interrogators, some of them CIA personnel and civilians who had worked elsewhere. Soldiers and interrogators took those methods to a criminal extreme. That they were able to do so shows that the harm Mr. Gonzales warned of but ultimately dismissed -- the undermining of U.S. military culture -- came to pass. Repairing it will require Mr. Bush -- or Congress -- to reverse his harmful decision to distort the rule of law.