Most of the questions had already been asked before Sen. Lindsey O. Graham (R-S.C.), one of the Senate Armed Services Committee's most junior members, got his chance. "Saddam Hussein is in our control. How would you feel if we sicced dogs on him tomorrow?" Graham asked Maj. Gen. Antonio M. Taguba, author of the now-famous report documenting abuse of Iraqi prisoners.

"Sir, we still have to follow the tenets of international law," the general responded. Graham agreed and then asked with exasperation: "What are we fighting for . . . to be like Saddam Hussein?"

A few days later, Sen. Jack Reed (D-R.I.) had been listening for several hours to Deputy Defense Secretary Paul D. Wolfowitz when he had heard enough. "What I've heard from you is dissembling and avoidance of answers," Reed snapped. Wolfowitz denied the charges, but Reed persisted. "Well, I would suggest, Mr. Secretary, that you're not doing your job," Reed said.

With questions and commentaries like these, the two back-bench senators have moved into the national spotlight as key players in the congressional inquiries into abuse of Iraqi prisoners by American soldiers.

On the surface, they could not be more different: a southern conservative and a New England liberal who disagree on most major issues that come before Congress. But they share a military background, keen intellect and the discipline to put aside their strongly held political views when it comes to national security matters.

Graham, 48, a former military lawyer, was elected to the Senate in 2002 after four terms in the House, where he took a leading role in the impeachment of President Bill Clinton. He is regarded as a rising star in the GOP, reliably conservative on most issues but with a sharp tongue, quick wit and fiercely independent streak that are beginning to draw attention.

Reed, 54, a West Point graduate with eight years as an infantry officer, moved to the Senate in 1997 after three terms in the House and is about as liberal as Graham is conservative. Earnest, serious and considerably more reserved than Graham, Reed has become an influential voice on military issues, especially among Democrats.

In contrast to many of their more patrician colleagues, both came from blue-collar backgrounds -- Reed's father was a school custodian, and Graham's parents owned what he describes as a "beer joint" -- which helps explain one of their common objectives.

"I'm not going to sit on the sidelines and see a bunch of privates thrown to the wolves," said Graham. "I want to ensure we don't just look down the chain of command but up the chain to the very highest level," said Reed.

Together with some other relatively new members, such as Sen. Hillary Rodham Clinton (D-N.Y.), who is also an aggressive questioner, Graham and Reed have helped give the committee a sharp edge as it moves into one of its highest-profile roles since the end of the Cold War.

"They're independent, they put patriotism above politics, and they're smart," said Michael E. O'Hanlon of the Brookings Institution, who formerly dealt with military issues for the Congressional Budget Office.

At a time when lawmakers are being criticized for haphazard oversight efforts and for failing to probe deeper into early policies on Iraq, the inquiry into prison abuses is earning praise.

"They were very accepting of what was put before them before the invasion of Iraq," said F. William Smullen, who spent 30 years in the Army, served as an aide to Secretary of State Colin L. Powell and heads national security studies at Syracuse University's Maxwell School. Now, he said, "they're acquitting themselves well."

To colleagues, Graham and Reed have also brought a helpful level of expertise and commitment, without the sharp partisanship that pervades many Senate operations as the elections approach.

"Both Senators Reed and Graham bring not only experience in the military but also their sense of obligation and duty arising out of that experience . . . a level of expertise and concern that is not partisan," Clinton said. "When I listen to them, I'm always impressed at how they raise the level of debate and discourse."

During hours of hearings over the past week, the two senators asked some of the toughest questions. Reed repeatedly pressed Defense Secretary Donald H. Rumsfeld and others about who approved practices aimed at softening prisoners for interrogation. Graham wanted to know why the president, Congress and the secretary of defense were not informed earlier of the photos of prisoner abuse.

The seriousness of the issue "has focused both of us on what we have in common rather than our disagreements," Graham said. "Our blood boils when we see command irresponsibility."

"Jack is very analytic in his questions. He tries to gather information like putting together pieces of the puzzle . . . I try to paint a big picture, paint what the big issues are," Graham added. "So we complement each other."

Reed voted against the 2002 resolution authorizing war in Iraq, while Graham voted for it. Both supported the $87 billion funding bill in 2003 for postwar operations in Iraq and Afghanistan. Both have indicated impatience with Rumsfeld, but neither has called for his resignation.

Graham and Reed are unusual in today's Senate in that relatively few new senators have military experience, and none as extensive as theirs. As the big World War II generation of veterans has grown older, the number of senators with military experience has declined. Of the 21 senators first elected in the 2000 and 2002 elections, only Graham and four others had military experience.

After receiving his law degree from the University of South Carolina, Graham served as both prosecutor and defense counsel for the Air Force for 61/2 years. In his most celebrated case, he successfully defended an accused officer by exposing flaws in the Air Force's drug-testing program, a story carried on CBS's "60 Minutes." Now a member of the Air Force Reserve, he has served as a judge advocate and was called up for the Persian Gulf War but did not go abroad.

After graduating from West Point, Reed served in the 82nd Airborne, where he commanded paratroopers. He got a master's degree at Harvard's Kennedy School of Government and later graduated from Harvard Law School. He taught at West Point and now serves on its governing board. At West Point and the 82nd Airborne, he said, he got to know at least a dozen of the top military officials involved in the Iraq war and its aftermath, including Army Gen. John P. Abizaid, chief of the U.S. Central Command.