Hagel could do the tough, no-nonsense-boss part of the job. But Gates had another essential talent that will be harder to match. He was a genuine national-security intellectual, who had studied how to manage and motivate huge institutions when he was director of the CIA and at the National Security Council. He knew the big strategic things about defense policy, but he also knew the little technical things. Gates was such a sawed-off shotgun of a guy that it was easy to miss that he was also a subtle thinker.

Nobody who knows Hagel would describe him as a defense intellectual. He’s more blunt than nuanced. How would he steer Pentagon procurement decisions in this age of new technologies and strategic matrices? I’m not sure. How would he manage the chiefs in their knife fights over the budget? Again, I’m not sure…

If Hagel gets the job, he will need two things: First is a willingness to say no to the chiefs and their logrolling allies on Capitol Hill. I suspect he would do fine with that part. Second, he will need a partner on the order of Hamre, or former undersecretary Michèle Flournoy, who can serve as his deputy and chief operating officer and help him manage the immensely complex decisions about defense spending and strategy. Without such a partner, it would be hard for Hagel to succeed.