WASHINGTON (AP) — President Barack Obama's nominee for defense secretary on Thursday defended his views of the military and global threats in a combative confirmation hearing, pushing back against criticism of his past statements on Israel, Iran, Iraq and nuclear weapons. Chuck Hagel told senators that America "must engage — not retreat — in the world," and insisted that his record is consistent on that point.

The former two-term Republican senator faced strong GOP resistance and was forced to explain past remarks and votes even as he appeared on a path to confirmation as Obama second-term defense secretary and the nation's 24th Pentagon chief.

His fiercest exchange came with Sen. John McCain, R-Ariz., a fellow Vietnam veteran, onetime close friend and a potential vote that would carry considerable sway. Politics and Hagel's evolving opposition to the Iraq war caused a split between the two men that was on full display at the confirmation hearing.

McCain pressed Hagel on whether he was right or wrong about his opposition to the influx of 30,000 U.S. troops in Iraq in 2007. Hagel, who voted to authorize military force in Iraq, later opposed the conflict, comparing it to Vietnam and arguing that it shifted the focus from Afghanistan.

"Were you right? Were you correct in your assessment?" McCain asked.

"I would defer to the judgment of history to sort that out," Hagel said as the two men talked over each other.

"The committee deserves your judgment as to whether you were right or wrong about the surge," McCain insisted.

Unable to elicit a simple answer, McCain said the record should show that Hagel refused to answer.

McCain made it clear that he would have the final word — with his vote, which he said would be influenced by Hagel's refusal to answer yes or no.

"I think history has already made a judgment about the surge, sir, and you're on the wrong side of it. And your refusal to answer whether you were right or wrong about it is going to have an impact on my judgment as to whether to vote for your confirmation or not," he said.

Hagel was the lone witness in a jam-packed hearing room at a session that could be crucial in determining whether he will win Senate confirmation and join Obama's second-term national security team. He spoke out forcefully for a strong military while trying to explain 12 years of Senate votes and numerous statements.

"No one individual vote, no one individual quote or no one individual statement defines me, my beliefs, or my record," Hagel told the Senate Armed Services Committee. "My overall worldview has never changed: that America has and must maintain the strongest military in the world; that we must lead the international community to confront threats and challenges together; and that we must use all tools of American power to protect our citizens and our interests."

Hagel, 66, a decorated Vietnam combat veteran, would be the first enlisted man to become defense secretary, a point that Armed Services Committee Chairman Carl Levin, D-Mich., highlighted.

"It would be a positive message for our soldiers, sailors, airmen and Marines in harm's way around the world to know that one of their own holds the highest office in the Department of Defense and that he has their backs," Levin said.

Two former committee chairmen — Democrat Sam Nunn and Republican John Warner — introduced the nominee.

"War for Chuck Hagel is not an abstraction," Nunn said.

Hagel has the announced backing of about a dozen Democrats and the tacit support of dozens more who are unlikely to embarrass the president by defeating his Cabinet pick. One Republican — Sen. Thad Cochran of Mississippi — has said he will vote for his former colleague.

Six Republicans, including four members of the Armed Services panel, have said they will oppose Hagel's nomination. Sen. Jim Inhofe of Oklahoma, the top GOP lawmaker on the committee and an opponent of Hagel, almost immediately complained that Hagel had not provided to the committee all of his speeches over the last five years, as requested.

Inhofe said Hagel's record "is deeply troubling and out of mainstream views."

In a later exchange with Sen. Bill Nelson, D-Fla., Hagel sought to explain that his wartime experience in which he was wounded twice informed his decisions and votes.

"It does condition you," he said. "I'm not shaped, framed, molded, consumed by that experience. Of course not. But it's part of me."

Hagel would be the lone Republican in the Obama Cabinet if the Senate confirms him, but the prospect has failed to placate GOP senators in a post-election atmosphere that remains as politically divisive as the fierce 2012 campaign.

Once the hearing was under way, the Republican National Committee put out a news release titled, "Chuck Hagel is the Wrong Choice for Secretary of Defense," and contending that he would weaken the nation's military.

Responding specifically to attacks from outside GOP-leaning groups, Hagel repeated his regrets about using the term "Jewish lobby" to refer to pro-Israel groups. He said he should have used another term.

Hagel said he was committed to Obama's goal of ensuring that Iran does not obtain a nuclear weapon, and insisted that all options, including military force, are on the table.

"My policy is one of prevention, and not one of containment — and the president has made clear that is the policy of our government," Hagel said.

Under questioning, Hagel said he always supported multilateral sanctions against Iran, but acknowledged that he cast votes against unilateral sanctions on a case-by-case basis. He argued that in some cases, such as votes in 2001-2002, he was taking into account the concerns of Republican President George W. Bush.

He also countered with votes and letters against Iran and Hezbollah.

"There's a more complete record than just one or two or three or four" votes, Hagel said, insisting that he has been on the record many times saying Hamas and Hezbollah are terrorist organizations and Iran is a state sponsor of terrorism.

He also expressed support for maintaining a strong, modern nuclear arsenal, a position that has been challenged because of his support for the Global Zero organization's recommendation of nuclear cuts.

"We are not going to unilaterally disarm," Hagel said.

The hearing was the first time Hagel publicly addresses the criticism that he is not sufficiently pro-Israel or tough enough on Iran. In the past, Hagel has questioned the efficacy of unilateral sanctions on Iran, arguing that penalties in conjunction with international partners made more sense.