Sometimes, this more centralized White House system becomes overwhelmed. “There’s a real choke point,” said Michèle Flournoy, who served as the Under Secretary of Defense for Policy, the No. 3 Pentagon civilian, in Obama’s first term. “There’s only so much bandwidth and there’s only so much they can handle at one time. So, things start to slow down.”

Flournoy and other former officials who criticize the administration’s approach concede that the most important decisions—using military force—must ultimately be the president's call. They argue, though, that intensified White House control has resulted in the United States being behind the curve, whether in trying to counter Russian propaganda about the Ukraine crisis or battling online recruitment by jihadists.

Syria, where the estimated death toll has topped 190,000, is cited as a prime example. By the fall of 2012, covertly arming Syria’s rebels had been accepted by Obama’s top three national-security Cabinet members—Clinton, Panetta, and CIA chief David Petraeus—as the best way to slow radicalism in Syria. The president and his inner circle first rejected the advice, then mounted a small-scale program to arm the rebels, and now, two years later, after Islamic State has seized swaths of Syria and Iraq, embrace the approach.

Obama’s aides say tight White House coordination is a must in an era when the United States faces threats like terrorism, which requires harnessing the capabilities of the Pentagon, the U.S. intelligence community, the State Department, and other agencies. It’s the president’s duty to take ultimate responsibility for matters of war and peace, they say.

“Other than, of course, the men and women in uniform” and other officials deployed abroad, said Ben Rhodes, a White House deputy national security advisor, “only the president of the United States is assuming the risk of the cost of action."

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This account of Obama’s national-security decision-making is based on interviews with more than 30 current and former U.S. government officials, who have served both Democratic and Republican administrations going back to President Richard Nixon.

In some ways, Obama’s closer control and the frequent marginalization of the State and Defense departments continues a trend begun under Bill Clinton and George W. Bush. But under Obama, the centralization has gone further. It was the White House, not the Pentagon, that decided to send two additional Special Operations troops to Yemen. The White House, not the State Department, now oversees many details of U.S. embassy security—a reaction to Republican attacks over the lethal 2012 assault on the U.S. consulate in Benghazi, Libya. A decision to extend $10 million in non-lethal aid to Ukraine also required White House vetting and approval.

On weightier issues, major decisions sometimes catch senior Cabinet officers unawares. One former senior U.S. official said Obama’s 2011 decision to abandon difficult troop negotiations with Baghdad and remove the last U.S. soldiers from Iraq surprised the Pentagon and was known only by the president and a small circle of aides.