Sen. Bill Nelson (D-Fla.) asked Chuck Hagel if he was wounded in Vietnam. Hagel said he did not want to dwell on his personal history (he was wounded, by shrapnel) but would instead explain how Vietnam shaped his own worldview.

"It doesn't mean I'm any better, doesn't mean I'm any smarter, doesn't mean I'm any more appreciative" of our troops, Hagel said. But "I saw it from the bottom, I saw what happens, I saw the suffering and the horror of war."

"So I did question the surge," he said, referring to his earlier exchange with Sen. John McCain (R-Ariz.). "I always ask the question, 'Is this going to be worth the sacrifice?'" In the case of the surge, he said, "I'm not sure, I'm not that certain that it was required."

He went on to emphasize that Vietnam is not his only frame of reference. "I don't see the lens of every world event ... through the lens of Vietnam," he said. "It is part of me, it is part of that lens. I think that's for the better."