BACK IN MAY Sen. John W. Warner (R-Va.), chairman of the Senate Armed Services Committee, vowed to continue probing the abuse of detainees in Iraq despite pressure from leading congressional Republicans to stop. Since then he hasn't held a single public hearing, partly because of a prolonged Senate debate over the annual defense authorization bill but also because of the Bush administration's resistance to supplying key witnesses and documents. Mr. Warner's staff says the committee will have a closed meeting with the Pentagon this week to discuss the status of official investigations and hopes to hold at least one public hearing before the congressional recess begins at the end of this month. This is welcome news: There remain many unanswered questions about the criminal mistreatment of prisoners in Iraq, Afghanistan and elsewhere -- and the Bush administration's continued stonewalling makes congressional action essential.

The White House took a step toward openness last month by repudiating parts of a legal opinion that justified torture and by releasing the current interrogation procedures at the Guantanamo Bay prison. But the administration clings to the myth that prisoner abuse was limited to a handful of low-ranking military personnel, and it shamefully seeks to shield senior military and civilian officials from accountability. Mr. Warner has asked for the testimony of seven high-ranking officers or Pentagon political appointees, only to be rebuffed on the pretext that their appearance might compromise ongoing investigations.

Meanwhile, a key report promised to Congress on the actions of Army intelligence personnel has been delayed, and key documents requested by Armed Services have not been delivered -- though senators may finally be able to review previously undisclosed Red Cross reports on Iraq at this week's meeting.

Pentagon officials point to numerous continuing criminal and administrative investigations, including one review led by two former defense secretaries and a former member of Congress. Yet none of these may answer crucial questions surrounding two senior Army officers: Lt. Gen. Ricardo S. Sanchez, the former Iraq theater commander, and Maj. Gen. Geoffrey D. Miller, the former commander at Guantanamo who now supervises Iraqi prisons. Both testified under oath to the Armed Services Committee in May that they had nothing to do with a set of "rules of engagement" posted at the Abu Ghraib prison last year. But other testimony and documents show that most or all of those interrogation techniques were listed in a policy issued by Gen. Sanchez's office, following the recommendations of Gen. Miller. Gen. Miller's testimony is contradicted by sworn statements given to an Army investigative team in Iraq. The accountability of these two generals for the illegal procedures adopted at Abu Ghraib must be fully investigated and publicly clarified -- particularly as Gen. Miller continues to oversee sensitive prison operations.

Congress also has a duty to probe more deeply into the actions of Secretary of Defense Donald H. Rumsfeld and former CIA director George J. Tenet. Mr. Rumsfeld stated publicly last month that at Mr. Tenet's request he ordered that several prisoners in Iraq not be registered with the International Red Cross, as required by the Geneva Conventions. As an official Army report put it, this was "contrary to Army doctrine and in violation of international law." If, in fact, Mr. Tenet and Mr. Rumsfeld conspired to violate the Geneva Conventions in Iraq, they should be held accountable -- just like the lowly reservists whom the Pentagon now prosecutes.