US Secretary of Defence Chuck Hagel has announced his resignation after two years at the helm, in a move that is sure to raise questions over the status of a slew of critical US military commitments - including the fight against the Islamic State in Iraq and Syria (ISIS), the effort to contain the Ebola outbreak and the US Navy's continued engagement in Asia.
Mr Hagel made his shock announcement in the White House this morning with President Barack Obama and Vice President Joe Biden by his side. And though the remarks from both the president and Mr Hagel were pleasant and full of praise for each other, neither offered an explanation for the sudden departure. Mr Hagel received a hearty round of applause from the gathered reporters and even hugged the president before the cameras.
"Over nearly two years, Chuck has been an exemplary Defence Secretary, providing a steady hand as we modernized our strategy and budget to meet long tem threats while still responding to immediate challenges like ISIL and Ebola,"said Mr Obama.
"Last month, Chuck came to me to discuss the final quarter of my presidency and determined that, having guided the department through this transition, it was an appropriate time for him to complete his service."
Mr Hagel said he would stay on at the job until a successor is confirmed by confirmed by the Senate. Among the names that have already been thrown up are former undersecretary of defence for policy Michele Flournoy, former Pentagon official Ashton Carter and Democratic Senator Jack Reed.
To Mr Obama and Mr Biden, the outgoing Defence Secretary said he wanted to acknowledge their "leadership and friendship".
"I will continue to support you, Mr President, and the men and women who defend this country every day so unselfishly," the 68-year-old Mr Hagel said. "It's been the greatest privilege of my life to lead, and most importantly, to serve."
Mr Hagel's tenure at the Pentagon has featured some of the stiffest recent challenges the military has had to face. He oversaw the drawdown of troops from Afghanistan, a long ongoing battle against insurgents in Iraq and Syria and a large deployment to help contain the Ebola outbreak in West Africa - all the while juggling a large cut in the US military budget.
Mr Hagel has also been a strong supporter of the military aspect of the US rebalance to Asia. He hosted the first ever meeting of US and Asean defence ministers in Hawaii earlier this year.
Of late, however, there has been talk of growing disagreement between the secretary and the president especially over Mr Obama's "no boots on the ground" policy in Iraq and Syria. Mr Hagel had both publicly and privately declared a need for at least some troops with a combat role in the region. While there was no sign of tension at the resignation announcement, talk in the US capital swirled that the Defence Secretary had been pushed out of his job.
The first signs of trouble emerged last month when Mr Hagel's planned tripped to Vietnam was cancelled at the last minute, although talk then was that the secretary had too close a relationship with the president to be in jeopardy.
Mr Hagel is the currently the only Republican in Mr Obama's national security team and analysts are split over how much of a change in policy a new Pentagon chief would bring. On the one hand, the need to get the new defence chief approved by a Republican-controlled Senate would likely mean whoever comes next will take a more hawkish stance than Mr Hagel. On the other hand, there are those who don't believe there will be any significant shifts in policy given that the White House controls national security and defence policy, with the defence secretary simply in charge of executing it.
Congress was quick to pay tribute to the outgoing secretary. Senator John McCain released a statement saying: "Secretary Chuck Hagel and I have had our differences over many years, but I have always considered him a friend, a patriot, and a dedicated public servant who has always put our country first and the needs of our men and women in uniform above his own."