As the Defense Department looks to the future, how many of its pieces — redundant air forces and duplicate armies among them — are really needed for the nation’s security? How many fall into the nice-to-have basket that might no longer be affordable? The topic gets kicked around by John Nagl of the Center for a New American Security and your Battlelander, along with Dave Barno, a retired Army lieutenant general, and Nora Bensahel, a military strategist at CNAS.