But Reps. Gary Ackerman, D-N.Y., Robert Melendez, D-N.J., Rep. Robert I Wexler, D-Fla., and Sherrod Brown, D-Ohio, challenged Powell about the administration's case, suggesting it may have been misleading from the outset.
"Truth is the first casualty of war," Ackerman said. "I would contend truth was murdered before a shot was fired."
"We went into this war under false premises," Melendez said.
Wexler told Powell he considered him to be "the credible voice in the administration."
"When you reached the conclusion that Iraq represented a clear and present danger to the United States, that meant a lot to me," Wexler said. "But the facts suggest there was a part of the story that was not true."
Powell fielded the assertions calmly, defending the president's judgment and his own.
But when Brown contrasted Powell's military experience to Bush's record with the National Guard, saying the president "may have been AWOL" from duty, Powell exploded.
"First of all, Mr. Brown, I won't dignify your comments about the president because you don't know what you are talking about," Powell snapped.
"I'm sorry I don't know what you mean, Mr. Secretary," Brown replied.
"You made reference to the president," Powell shot back.
Brown then repeated his understanding that Bush may have been AWOL from guard duty.
"Mr. Brown, let's not go there," Powell retorted. "Let's not go there in this hearing. If you want to have a political fight on this matter, that is very controversial, and I think it is being dealt with by the White House, fine, but let's not go there."
Powell then went on to defend the Bush administration's assertions on Iraq's pre-war weaponry. "We didn't make it up," Powell said. "It was information that reflected the views of analysts in all the various agencies."