On Monday President Obama nominated Gen. Martin E. Dempsey, the Army chief, as the next chairman of the Joint Chiefs of Staff, the country’s highest-ranking military officer, the New York Times reports. Obama also promoted two other senior military leaders, effectively overhauling leadership at the Pentagon, which has been led thus far by George W. Bush appointees.

While Obama praised Dempsey during the nomination, Dempsey was not believed to be the president's first choice, according to the Washington Post. For more than a year, Obama had favored Marine Gen. James E. Cartwright, the vice chairman of the Joint Chiefs, one of his most trusted military advisers, whose current term ends in August. But on May 21, Obama informed Cartwright that he wouldn’t get the job, and picked Dempsey, who had only recently assumed the position of Army chief.

The Influence of Robert Gates. While the Times indicates that "questions of personnel management and command style pushed [Cartwright] out of the running," the Post writes that it was "because of opposition from Defense Secretary Robert M. Gates and outgoing chairman Adm. Mike Mullen, who butted heads with Cartwright over strategy for the war in Afghanistan." Gates and Mullen are both Bush administration holdovers.

David Wood at the Huffington Post writes that Cartwright, despite being "a personal friend" of Obama's, was mistrusted by "much of the Pentagon brass."

His chilly relations inside the building stemmed in part from his role during the administration’s long and bitter debate in the fall of 2009 over Afghanistan war strategy. Cartwright worked with Vice President Joe Biden to help develop an option for a smaller troop presence, while the the Joint Chiefs and Defense Secretary Robert Gates were pushing for a major “surge’’ of troops.

Gates and Mullen's influence not only led Obama to drop Cartwright, but pushed him in the direction of Dempsey. The Times notes that officials said "the high opinion Mr. Gates has of General Dempsey — one shared by Admiral Mullen — was a significant factor in shaping Mr. Obama’s decision." A few days ago, Thomas Ricks asked at Foreign Policy, "Why is Gates leading making the choice, instead of [C.I.A. Director] Panetta, the guy who will have to work with him?"

The Misconduct Investigation. The Pentagon investigated Cartwright over claims of misconduct with a young female aide, according to the Army Times. No doubt this hurt his chances, although the Pentagon’s inspector general cleared Cartwright of the most serious claims, which suggested he’d had an improper relationship with the woman. "But the investigation found that he mishandled an incident in which the aide was drunk and either passed out or fell asleep in his hotel room, where he was working, as his security personnel stood nearby."

Combat Experience. Dempsey seems the safer choice. He "has no vocal critics across the armed forces," reports the Times, and "carries a reputation for a much more collegiate style of leadership," according to the Post. But perhaps more importantly, Cartwright has never led ground troops in combat, whereas Dempsey has. "With nearly 40 years in uniform, [Dempsey] is one of our nation's most respected and combat-tested generals," Obama said when he made the announcement on Monday.

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