Defense Secretary Chuck Hagel resigned Monday amid reports of his "frustration" with the White House administration on the strategy for Iraq and Syria.
"You should know that I did not make this decision lightly," Hagel said at a hastily-arranged announcement of his resignation at the White House with President Obama and Vice President Joe Biden.
"It's been the greatest privilege of my life" to serve as secretary of defense, Hagel said. "After much discussion, the President and I agreed that now was the right time for new leadership here at the Pentagon."
A senior Defense Department official said that Hagel and Obama agreed that a change in military leadership would be best for the nation at a time of crisis overseas and budget uncertainty.
"It was mutual," the official said of the decision to resign.
Hagel said he would stay on as the defense secretary until a successor is confirmed by the Senate in what promises to be contentious hearings before the new chairman of the Senate Armed Services Committee, Sen. John McCain, R-Arizona.
Obama pledged a quick decision on a nominee to succeed Hagel, who served for less than two years. Hagel was the first enlisted combat veteran from Vietnam to lead the Pentagon.
Among the possible successors said to be on the short list of the White House were Michelle Flournoy, the former undersecretary of Defense for policy, current Deputy Defense Secretary Robert Work, and former Deputy Defense Secretary Ashton Carter.
Flournoy would be the first woman to lead the Defense Department.
Sen. Jack Reed, D-Rhode Island, a West Point graduate and former Army Ranger, was also rumored as a possible successor but he has stated that he wishes to remain in the Senate, where he would be the ranking Democrat on SASC.
McCain said that Hagel came to his office last week to vent on problems that he and Gen. Martin Dempsey, the chairman of the Joint Chiefs of Staff, were experiencing with Obama, White House National Security Adviser Susan Rice and others on Obama's closely-knit policy team.
McCain said that "Chuck was frustrated with aspects of the Administration's national security policy and decision-making process."
McCain said that Hagel's "predecessors have spoken about the excessive micro-management they faced from the White House and how that made it more difficult to do their jobs successfully. Chuck's situation was no different."
McCain was referring to the remarks last week by former Defense Secretaries Robert Gates and Leon Panetta at the Reagan National Defense Forum in California.
Gates likened Obama to former President Lyndon B. Johnson in what he called the "micromanagement" of military policy and targeting during the Vietnam War.
"It was micromanagement that drove me crazy," Gates said in describing members of Obama's NSC staff who directly called four-star generals on matters of strategy and tactics.
Panetta singled out the current campaign against the Islamic State of Iraq and Syria (ISIS) in which Obama has ruled out the use of ground combat troops.
"Never tell your enemy what the hell you're going to do," Panetta said.
A senior Defense Department official, speaking on background, denied that Hagel was frustrated with Obama or his staff.
"He is frustrated that Congress has not been able to lift the yoke of sequester," a reference to the Congressional actions under the Budget Control Act that have mandated drastic cuts for the military.
The official said that Hagel initiated several discussions with Obama starting last month on the way forward in the last two years of the administration and they both decided on the need for new leadership at the Pentagon.
"It was not about a disagreement, it was not about a resignation in protest, it was not about him running out of gas," the official said.
The official likened Hagel to a starting pitcher in baseball in need of relief. "Sometimes that means going to the bullpen," the official said. "Sometimes being a leader means knowing when it's time to go."
In his own statement on the resignation, Dempsey said that Hagel "brought a soldier's heart to work every day. He cared deeply for our young men and women in uniform, and they had no greater advocate."
Hagel "led the military at a particularly difficult time in our history," Dempsey said. "He set us on course for many lasting reforms" on the budget, pay and compensation, women in combat, the rebalance to the Pacific, cybersecurity and combating sexual assaults in the ranks.
At the brief ceremony in the White House Dining Room, Obama said Hagel came to him last month to state that "it was an appropriate time for him to complete his service." Obama thanked Hagel for his "exemplary service" and gripped him in a bear hug before they exited without taking questions.
Hagel's resignation came amid increasing rumors of friction recently with the White House staff, and particularly with National Security Adviser Susan Rice, that began with Hagel's abrupt cancellation last month of a long-planned trip to Vietnam and Burma.
It would have been Hagel's first visit as Defense Secretary to Vietnam, where he served as a sergeant in 1967-68 with the Army's 9th Division and was wounded twice.
Both Hagel and Dempsey reportedly have had difficulty on occasion getting their views past the White House staff to Obama.
As the President's top military advisor, Dempsey has denied lacking access to Obama but he confirmed jumping uninvited into the President's limo last month after a State Department meeting to discuss Iraq personally with Obama.
Hagel confirmed writing a two-page memo to Rice to get across his and Dempsey's views on the way forward in Iraq and Syria against the Islamic State of Iraq and Syria.
Hagel and Dempsey have repeatedly stressed an "Iraq first" strategy while the White House was said to be concerned about also confronting the regime of Syrian President Bashar al-Assad.
At a news conference last month, Hagel defended writing the memo.
"We owe the President and we owe the National Security Council our best thinking on this, and it has to be honest and it has to be direct," Hagel said.
Since the Republicans' sweeping victories in elections earlier this month, Pentagon officials had sought to dispel rumors that Hagel would be stepping down as Obama sought to bring in a new term for his final two years in office.
In an interview last week with Charlie Rose on PBS, Hagel sidestepped questions on whether he had lost Obama's confidence and said "I serve at the pleasure of the President."
The apparent dispute with the White House staff was only the latest in a series of confrontations that have marked Hagel's tenure at the Pentagon. The confrontations began even before he was formally confirmed in February 2013.
The SASC vote to confirm him was 14-11, unusually close for a high-ranking nominee, and the vote on the Senate floor was held up by a filibuster – the first time in the history that a Defense Secretary's nomination was filibustered.
"It's a real tragedy, a tragedy for Hagel and for the country," Lawrence Korb, a former assistant secretary for personnel at the Pentagon, said of Hagel's resignation.
Korb speculated that Hagel never fully recovered from his bruising Senate confirmation hearing in which he was challenged on policy and his commitment to the defense of Israel. "That put him in a very difficult position," said Korb, an analyst at the Center for American Progress.
-- Richard Sisk can be reached at email@example.com