Washington convention dictates that all sides in the debate on Iraq begin by stipulating that U.S. armed forces have performed "magnificently" and "heroically," and, implicitly, bear no blame for any of the messes. Perhaps that's mostly true -- but the boilerplate rhetoric risks perpetuating a culture of impunity among senior American military commanders.

The sad truth is that since the beginning of the war on terrorism, top U.S. officers have responded to sometimes tragic mistakes or wrongdoing in Afghanistan and Iraq with defensive stonewalling -- and gotten away with it. Early on, the Army refused to acknowledge error, much less assign responsibility, for a June 2002 helicopter attack on an Afghan wedding party that killed about 46 civilians. Instead, a quick-march investigation cleared all involved. Until the furor caused by the release of the prison abuse photographs from Iraq, nothing was done about two Afghan detainee deaths in December 2002 that had been officially designated homicides.

Now the Pentagon boasts about the multiple investigations it has launched into the mistreatment of prisoners, which it describes as proof of its ability to self-police. But what of the senior commanders who oversaw this record and drew up the policies under which the crimes took place? For them, the standard procedure of evasion and denial still seems to be in effect.

Take Lt. Gen. Ricardo S. Sanchez, until recently the commander of all U.S. forces in Iraq. On May 19 Sanchez appeared before the Senate Armed Services Committee to discuss the crimes at Abu Ghraib and his own role in setting the policies for interrogating prisoners. His statements were made under oath. Yet a number of them are strikingly at odds with other sworn testimony and official documents.

The intelligence commander at Abu Ghraib, Col. Thomas Pappas, told an Army investigation that techniques for interrogating prisoners that clearly violate the Geneva Conventions, such as the use of dogs for intimidation and of sensory deprivation, were approved by Sanchez. An Abu Ghraib document backs him up, referring to a Sept. 10, 2003, "Interrogation and Counter-Resistance Policy" issued by Sanchez's headquarters. That document authorizes the use of a number of harsh techniques by interrogators with the approval only of the local officer in charge. It would seem to be an obvious part of the explanation for the photos depicting guards threatening prisoners with dogs.

Before the Senate, however, Sanchez claimed to know nothing about the techniques or their approval. Asked if he had "ordered or approved the use of sleep deprivation, intimidation by guard dogs, excessive noise and inducing fear," he replied: "I never approved any of those measures to be used within [the Iraqi theater] at any time in the last year."

"How could the company commander evolve such a specific list," pressed Sen. Jack Reed (D-R.I.). "Sir, it's difficult for me to understand it," was the general's response. "You'd have to ask the commander."

In fact, other testimony to Congress and the Army makes clear how the list came about. It was drawn up in early September by Sanchez and his legal office, on the recommendation of Maj. Gen. Geoffrey D. Miller, then the commander of the Guantanamo Bay prison, who arrived in Iraq with a mandate to improve intelligence collection at Abu Ghraib. According to Pappas, it was Miller who suggested the use of dogs to frighten prisoners -- even though the same technique had been banned at Guantanamo eight months earlier, after protests by Pentagon lawyers.

Pappas was asked by Army investigators how he reconciled the use of dogs with the Geneva Conventions. "I'll be honest, I never really -- I did not personally look at that with regard to the Geneva Convention," he replied. "It was a technique that I had discussed with General Miller when he was here. That particular idea came from Guantanamo Bay . . . I believe that we had [Sanchez's] approval to use dogs as long as, based on this memorandum, as long as they were muzzled."

Miller was also at that May 19 Armed Services hearing. He also testified under oath. He was asked about another Abu Ghraib document listing "interrogation rules of engagement," including the use of dogs. "The contents of that document were not briefed to me," he said of the procedures drawn up on his own recommendation. "I do not know what level that document was developed at."

Did Sanchez and Miller lie under oath to Congress? Perhaps not. Maybe they just carefully and legalistically avoided stating the truth -- which, according to the available evidence, is that the two of them are largely responsible for the adoption at Abu Ghraib of an interrogation policy including blatantly illegal methods. Either way, they are setting a less-than-heroic example for their Army of how to respond to mistakes and failures.

By the way: Since May 19 the Pentagon has refused to authorize further testimony by senior officers before Armed Services. Miller, meanwhile, is in Iraq -- where he commands all detention facilities, including Abu Ghraib.