Chuck Hagel, the US defence secretary, has resigned from his position after President Obama "reluctantly" accepted his request to step down.
Barack Obama made an announcement from the White House Rose Garden where he confirmed Hagel would leave after two years in the post. The move is widely seen as an attempt to signal a recognition of new threats to US security including IS, which require a different form of leadership.
Obama is widely viewed as losing confidence in Hagel but he was positive towards the man he picked for the role in late 2012, saying that "as reluctant as we are to see you go" he had accepted the resignation.
Hagel was a vocal critic of the Iraq war and was appointed to oversee the exit of American forces from both Iraq and Afghanistan. According to the New York Times, Hagel wasn't fired but reached a mutual agreement with President Obama to step down.
Hagel was the last Republican on Obama's national security team and is the first person to leave the President's cabinet since the Democrats' disastrous losses in the mid-term elections.
Speaking today, Hagel said: "I have today submitted my resignation as Secretary of Defence."
Hagel succeeded Leon Panetta as defence secretary in Obama's second term and had served as an infantry squad leader in Vietnam, winning two purple hearts.
He went on to serve as Senator for Nebraska. Hagel was the first US secretary of defence in history to have his appointment filibustered in the Senate after Democrats failed to secure enough Republican votes to end the debate on his nomination and take a final vote.