WASHINGTON ― President Barack Obama’s pick to be the next defense secretary, Ashton Carter, will inherit a tense relationship between the U.S. military and the White House that is unlikely to ease even with a fresh face at the Pentagon.

Carter, 60, a policy wonk with degrees in medieval history and theoretical physics, is a bona fide defense expert but also a blunt-spoken figure who could run into trouble with a White House said to be given to micro-management.

With years of experience in senior Pentagon posts, “it’s hard to imagine someone better prepared for this job,” said Stephen Biddle, a professor at George Washington University who knew Carter at Harvard.

“He’s widely respected among Pentagon civilians and the uniformed military.

He’s a capable, experienced manager. He’s breathtakingly smart,” Biddle told AFP.

But “there are big uncertainties with respect to Carter’s ability to shape U.S. defense policy under an administration this centralized.”

Carter will be expected to manage the U.S.-led air war against the Islamic State group in Iraq and Syria, but he will face White House aides who critics say have been unwilling to relinquish control of strategic questions.

Two former defense secretaries, Robert Gates and Leon Panetta, both complained bitterly in recently published memoirs that Obama’s White House distrusts the military and often tries to shut out the Pentagon from decision making.

Both men also accused the White House of taking decisions on troop numbers and strategy in Iraq and Afghanistan based more on political calculations than national security interests.

The outgoing Pentagon chief, Chuck Hagel, who announced his resignation last month, also became frustrated with meddling from the White House, officials and lawmakers said.

“There’s always some level of tension in civilian-military relations, but it’s been higher in this administration, there’s no question about it,” Biddle said.

The acrimony peaked during Obama’s first term as he weighed advice on the war in Afghanistan. After a protracted internal debate marked by incessant leaks, Obama opted to send more troops as the military requested, but also set a timeline for a rapid drawdown that is still a source of resentment for many commanders.

The White House on Thursday sought to play down the tension with the Pentagon during Obama’s tenure, saying such friction is “not unique to this administration.”

However, spokesman Josh Earnest stressed the next defense secretary will “understand that the president of the United States is the commander in chief and sits atop the chain of command.”

Carter’s views, however, have not always been in synch with the administration.

He favored keeping U.S. troops in Iraq, for instance, instead of withdrawing forces in 2011, and he has repeatedly warned of the dangers of scaling back defense spending.

“I’m sure he’ll want to be an architect and not just a carpenter,” Biddle said. “Whether he and the White House staff can co-exist is unclear to me.”

Carter’s background in academia, industry and Pentagon management resembles another former defense secretary who has also served as his mentor, William Perry, who was defense secretary during Bill Clinton’s presidency in the 1990s.

Perry has praised him as “superbly qualified.” But unlike Perry, Carter has a more assertive personality and some of his critics say he has an impatient side that can alienate some staff members.

Perry has described Carter as “hard-charging.”

“People who work for him who are not moving hard or fast tend to get run over by that,” Perry told the Washington Post.

“That was perhaps most manifest when he was deputy secretary of defense and basically kind of ran the Pentagon.”

If confirmed, Carter will arrive with an intimate knowledge of the Pentagon bureaucracy but he has never managed a war and has less experience with the volatile politics of the Middle East.

“By background, he is strongest on technology, nuclear and strategic issues, management, and acquisition policy. He is, as best I know, slightly less well prepared ― though hardly a novice ― on matters of the Middle East,” Michael O’Hanlon from the Brookings Institution said.

Until now, Carter has worked mostly out of the spotlight. (AFP)