Those themes match well with Obama’s vision for a national security policy that leans toward “soft power” approaches.

“To succeed, we must pursue a new strategy that skillfully uses, balances, and integrates all elements of American power: our military and diplomacy; our intelligence and law enforcement; our economy and the power of our moral example,” Obama said Monday.

Policy Differences

But Gates’ policy speeches also underscore several sharp differences with Obama. For example, Gates has repeatedly rejected strict timelines for troop withdrawals in Iraq, including Obama’s plan of removing all combat troops within 16 months.

Gates also has pushed strongly for developing a new type of nuclear warhead and moving forward with plans to deploy ballistic missile defense assets around the world — two initiatives that Obama has pledged to slow down.

Experts say Gates has a record of deferring to a president’s wishes when they contradict his own, especially since taking over for Rumsfeld at the end of 2006.

“Gates has been very malleable since he’s been in there,” said Lawrence Korb, senior fellow at the Center for American Progress.

For example, Gates was part of the Iraq Study Group, which called for a change in the U.S. mission and a drawdown of troops in Iraq in 2006. But after his appointment as Defense secretary, he wholeheartedly supported Bush’s so-called “surge” strategy, which sent another 30,000 ground troops to Iraq.

In 2008, Gates said he wanted to gradually reduce the level of U.S. troops in Iraq by the end of the year. But when Bush took the recommendation of Gen. David H. Petraeus, the top U.S. commander in Iraq, to halt any significant troop withdrawals, Gates again saluted.

“One would hope that Gates understands that by signing on that line he, in effect, will have to support Obama’s policies,” said Korb, “He can make his case, but if the president decides against them, he’s going to have to carry them out as Obama directs.”

Interest Groups Cautious

Some anti-war groups have complained that the Gates appointment runs counter to Obama’s campaign promises of change in Washington and speedy withdrawal from Iraq.

“I hoped a change in the administration would bring a change in the policy and keep my oldest son from being deployed next spring,” said Larry Syverson, a member of Military Families Speak Out, a group that is against the war, “That optimism diminished with the announcement that Robert Gates would continue to be the Secretary of Defense.”

Independent veterans groups expressed cautious optimism about the pick.

“For those who worry that Gates will somehow drag Obama to the right on Iraq, I think that fear is really unfounded,” Jon Soltz, co-founder and chairman of VoteVets.org, “Gates clearly understands that there will be a new course for our military, one that includes redeployment from Iraq, and wants to make it work. If he didn’t, he had a very nice private-sector life to which he could have returned.”

Gates is well known for having reluctantly taken the Defense job under Bush. He cited an obligation to serve when called upon by Bush to help during some of the darkest days of the Iraq war.

He has carried a stopwatch in his pocket these past two years, counting down the days until he could return to his post as president of Texas A&M University. But with Monday’s announcement, he said his sense of obligation to the troops drove him to rethink that timeline.

“I must do my duty as they do theirs. How could I do otherwise?” Gates said.

It is not clear who would work directly under Gates in the Pentagon’s top civilian echelon. Richard J. Danzig, an Obama adviser and a former Navy secretary, is considered a leading candidate for the deputy secretary post, although no announcement has been made to that effect.

Molly K. Hooper contributed to this story.