Defense Secretary Chuck Hagel has been forced to resign under pressure from President Obama less than two years after taking office. Obama announced Hagel’s departure on Monday.

President 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. Let me just say that Chuck is and has been a great friend of mine. I’ve known him, admired him and trusted him for nearly a decade, since I was a green-behind-the-ears freshman senator and we were both on the Senate Foreign Relations Committee.”

The announcement comes just weeks after a spokesperson for Hagel said he intended to remain in his post until the end of Obama’s presidency. Hagel had criticized the Obama administration’s war on the Islamic State in Iraq and Syria, writing in a leaked memo last month that the president’s policy could implode over a lack of clarity on Syrian President Bashar al-Assad. Hagel will keep his post until the Senate confirms his successor. Topping the list of contenders is Michèle Flournoy, a former undersecretary of defense who heads the think tank Center for a New American Security, which is funded mainly by military contractors. She would be the first woman to lead the U.S. military.