The decision was characterized as a mutual one by Hagel and President Obama, but I think this speaks volumes:
Mr. Hagel, a respected former senator who struck a friendship with Mr. Obama when they were both critics of the Iraq war from positions on the Senate Foreign Relations Committee, has nonetheless had trouble penetrating the tight team of former campaign aides and advisers who form Mr. Obama’s closely knit set of loyalists. Senior administration officials have characterized him as quiet during cabinet meetings; Mr. Hagel’s defenders said that he waited until he was alone with the president before sharing his views, the better to avoid leaks.Obama, whatever his other merits and flaws, is not comfortable with those who don't have a longstanding relationship with him. He's no Lincoln, who assembled his much-vaunted "team of rivals" to give him as broad a range of perspectives as possible. Intellectually Obama probably respects the need for differing points of view, but as a practical matter he has shown little stomach for having them represented among his closest advisors.
It's no secret that Obama has had a mixed record on foreign affairs. If the administration's foreign policy woes could be laid at the feet of an unprepared or undisciplined military, that would be one thing, but they can't. Nor has Hagel been irresponsibly cavalier in his management of the armed forces (unlike, say, Donald Rumsfeld).
Hagel, though, has made his share of gaffes articulating (or, more commonly, failing to articulate) administration policy, and that has made him a less effective spokesman for that policy than Obama would like. That failing alone justifies his dismissal, regardless of how well he has done his job behind the scenes. However, the message his dismissal sends is that Obama is casting about for relief from his woes, and he's not thinking very hard about what will do him the most good. Again, the military has not been primarily responsible for the administration's foreign policy troubles.
What Obama needs to fix is a troubling disconnection between rhetoric and action. An unfathomable failure to foresee the likely consequences of its rhetoric often means the administration is caught flat-footed by events. Syria is a prime example, Russia another.
To address the disconnection, Obama has to look long and hard at his national security and intelligence machinery. The most recent House committee report on the Benghazi attack implicated not the military or even the Administration (directly), but rather, the intelligence services' analysis of what was going on at the time. That's just one example of what's wrong.
Obama, however, will also have to look in the mirror. He hasn't been an effective salesman for his own foreign policy. Nobody seems to think his administration has a philosophy guiding its foreign policy. That may be unfair to the administration, but ultimately it's up to Obama to convince us otherwise. That failure is solely his. Firing Hagel isn't a great start to addressing that failure.