WASHINGTON (AP) — President Barack Obama’s nominee for defense secretary on Thursday defended his views of the military and global threats, pushing back against criticism that has focused on his past statements on Israel, Iran 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.

At his confirmation hearing, the former Republican two-term senator from Nebraska sought to defuse the barrage of criticism about his past remarks that GOP critics say showed a lack of support for a Middle East ally and complaints the he would weaken the military.

Hardly on an easy path and facing GOP resistance, Hagel sought to build support for his nomination to succeed Defense Secretary Leon Panetta and become the nation’s 24th Pentagon chief.

‘‘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.

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. 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.’’

Hagel’s most combative exchange came with Sen. John McCain, R-Ariz., a fellow Vietnam veteran, onetime close friend and a 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 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.

‘‘Well I’m not going to give you a yes or no. I think it’s far more complicated than that,’’ Hagel said.

McCain made it clear that he would have the final word — with his vote.

‘‘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.