Secretary of Defense Robert Gates

In the coming months, lots of people will be cranking up their computers and burning up the airwaves with commentary on the just-announced departure of Secretary of Defense Robert Gates sometime in 2011.

Evaluating his legacy as SECDEF when he ultimately leaves next year will be important for the historical record, but the challenges his yet-to-be-named successor will face are more important.

For instance, there’s little doubt that the war in Afghanistan will still be a major focus in 2011 — not to mention the challenge of managing the White House’s mandated draw down next summer. Don’t forget about Pakistan. Plus, with lots of American trainers likely still in Iraq next year, attention will need to be given to that region as well.

And there’s Iran, which will either be a nuclear-weapons state or darn close to being one by the time Gates leaves the E-Ring for the last time. Unfortunately, the current policy approach just isn’t making headway. The new secretary is going to face the less-than-amusing task of handling Tehran’s atomic ayatollahs.

Along the same lines, what will be the status of our missile defenses? An important matter, considering that they provide the best prospects for defending the homeland against the growing Iranian nuclear and ballistic-missile threat. They also protect our troops abroad and allies around the world — yet the program has been pushed back several years. Its success demands attention from the new Pentagon leader.

And what will be the state of our own aging nuclear deterrent — a force in desperate need of modernization — especially in light of the Senate’s consideration of the U.S.-Russia Strategic Arms Reduction Treaty (New START) this fall?

North Korea will likely be a continuing problem for the new SECDEF. The reclusive state has been more provocative recently than at any time since the end of the Cold War, sinking a South Korea warship this spring and unwilling to come to the table for talks. It’s also selling its nuclear know-how abroad in such places as Syria and Burma.

And, of course, there’s China. While most of the news has been on its newly-minted status as the world’s second-largest economy, Beijing has been spending lots of its yuan on developing a world-class military. For example, China now has the second-largest navy in the Pacific, after the United States. The chairman of the Joint Chiefs, previously curious, is now officially concerned.

Moreover, China’s unprecedented military build-up brings into greater fidelity the challenges of our own defense budget, margins of technological superiority, and the willingness of some allies to bear their share of the burden.

The responsibility pie isn’t shrinking, it’s growing — yet current defense budgets are projected to decline in the next few years. Gates’s successor would be wise to advocate, as he has, the idea that current defense spending levels are the bare minimum necessary to protect U.S. national interests.

In addition, the money saved from efficiencies and acquisition reform must be given back to the services by the SECDEF so they can modernize their war-weary and rusty arsenals with next-generation equipment.

The fact is that Secretary Gates’s successor will likely have a daunting inbox full of national-security challenges. As much as any other cabinet post, the defense secretary will need to display strong and skilled leadership from the first minute the new boss enters the Pentagon’s River Entrance.

Co-authored by Peter Brookes.

Cross-posted at The Corner.