He forged his views of war and the military as a young man in mine-plagued fields of Vietnam. Now Chuck Hagel may become the first Vietnam veteran and first enlisted soldier to serve as U.S. defense secretary.

In nominating him to succeed Leon Panetta, President Barack Obama urged the Senate to confirm a man he said "bears the scars" of that war and has the skill to guide the military through new challenges.

"Chuck Hagel is the leader that our troops deserve," Obama said.

If Hagel is confirmed, the Defense Department would be led by someone who advocated deep cuts to its budget. He's bucked his fellow Republicans in opposing troop surges in Iraq and Afghanistan, telling his biographer: "I will do all I can to prevent war." And he's come under fire over comments about Israel, a top American ally, and Iran, a top American foe.

Those issues and others have assured that the former Nebraska senator's path to the Pentagon won't be easy.

But Hagel said he's eager to answer critics.

Until Obama's announcement that ended weeks of speculation over his nomination, Hagel told the Lincoln Journal Star newspaper in his home state that he'd been "hanging out there in no-man's land unable to respond to charges, falsehoods and distortions" about his record.

Now, he said, he has "an opportunity to set the record straight."

"All I ask is a fair hearing, and I will get that," Hagel told the paper. "I am very much looking forward to having a full, open, transparent hearing about my qualifications and my record."

Carl Levin, who will chair those hearings as head of the Armed Services Committee in the Democratic-controlled Senate, praised Hagel's qualifications and said the panel would give "prompt and careful" consideration to his nomination.

Iraq, Iran, gay rights among hot-button issues

Hagel, 66, said Monday that he was honored Obama had "confidence in me and not unmindful of the immense responsibilities that go with it."

The current Georgetown professor and head of the Atlantic Council, a non-partisan international affairs group, praised troops who serve with "such dignity and selflessness."

Hagel promised to work to "strengthen our country's alliances and advance global freedom, decency and humanity" in the effort to "build a better world for all mankind."

At the same news conference where he announced the nomination of John Brennan as CIA director, Obama praised Hagel as a "patriot" who knows what it's like being on the frontline, in part from his year fighting alongside his brother in Vietnam.

"He understands that sending young Americans to fight and bleed in the dirt and mud is something that we only do when it's absolutely necessary."

The president, a Democrat, also said Hagel's selection "represents the bipartisan tradition that we need more of in Washington."

But many in the GOP establishment begged to differ.

"He has long severed his ties with the Republican Party," Sen. Lindsey Graham, R-South Carolina, said Sunday, when news surfaced that Hagel would be nominated.

Sen. Chris Murphy, a freshman Democrat from Connecticut, countered that he believes "Republicans are spoiling for a fight."

A host of issues swirling around Hagel have set the stage for a contentious confirmation hearing with Republicans expected to lead the charge against him.

A few years after famously bucking his party in opposing a U.S. troop "surge" in Iraq, Hagel voted against sending 30,000 additional troops in 2009 to Afghanistan -- a move that put him at odds with Republicans and Obama.

Some also are bothered by a comment he made in 1998 about an ambassadorial candidate James Hormel being "openly, aggressively gay" -- which he apologized for in December, 14 years later. This issue is compounded by the fact that Hagel could oversee a military that recently dropped its "Don't Ask, Don't Tell" policy for gay and lesbian personnel, a policy he supported.

The Log Cabin Republicans, a group that supports gay rights, called the Hormel apology "too little, too late." Yet gay rights activist Rick Jacob stood behind Obama and said "no one trying to derail (Hagel's) nomination attacks his qualifications."

Hagel has also come under fire over Iran.