Breaking: Chuck Hagel stepping down as defense secretary under pressure

The officials described Mr. Obama’s decision to remove Mr. Hagel, 68, as a recognition that the threat from the Islamic State would require a different kind of skills than those that Mr. Hagel was brought on to employ. A Republican with military experience who was skeptical about the Iraq war, Mr. Hagel came in to manage the Afghanistan combat withdrawal and the shrinking Pentagon budget in the era of budget sequestration.

But now “the next couple of years will demand a different kind of focus,” one administration official said, speaking on the condition of anonymity. He insisted that Mr. Hagel was not fired, saying that he initiated discussions about his future two weeks ago with the president, and that the two men mutually agreed that it was time for him to leave.

But Mr. Hagel’s aides had maintained in recent weeks that he expected to serve the full four years as defense secretary. His removal appears to be an effort by the White House to show that it is sensitive to critics who have pointed to stumbles in the government’s early response to several national security issues, including the Ebola crisis and the threat posed by the Islamic State.