It's also fair to ask whether we need as many troops. How likely is it that we're going to fight a large land war, or engage in a major naval battle, or fight air duels over contested territory, anytime soon?
Obviously, the future is uncertain, but it's not imponderable. Budgets, by nature, are in part about managing risk. Defense budgets require a different calculus of risk; the consequences of disaster can be catastrophic for the entire nation, so it's worth paying more to avert disasters, even those that have a very small chance of occurring. But how much more is it worth paying? How far down the list of extremely unlikely catastrophes do we want to keep covering? And what exactly does it take to cover those contingencies anyway?
"To infinity" is not the answer to any of these questions. But it's been a half-century since anyone asked them in a broad, systematic way. (In the last two years, Robert Gates asked some of them, and acted on the answers, in terms of several specific weapons systems, most notably the Air Force's F-22 fighter and the Army's high-tech Future Combat Systems vehicle. But, for a variety of reasons (some political, some temperamental, and some simply because a defense secretary can have only so much tsuris on his plate), he stopped short of applying the standards to larger issues of roles, missions, or the overall size and structure of the Army, Navy, Air Force, and Marines.
Gates' replacement, Leon Panetta, may wind up staring at a plate overflowing with slop, much of it indigestible, but there's no choice but to gulp and dig in. Panetta said, in a letter to the troops and his staff on Wednesday, that "across-the-board defense cuts"—which would be mandated if Congress fails to agree on a second round of debt-ceiling limits later this year—"would do real damage to our security, our troops and their families, and our ability to protect the nation." (Italics added.)
If that's true, he and his staff should start coming up with targeted cuts. Some questions they might ask: Does the Army really need 570,000 active-duty soldiers? Does the Air Force really need more F-35 Stealth aircraft (funded at $11 billion, for 43 more planes, next year alone)? Does the Navy really need $4 billion for two more Virginia-class submarines, or $1 billion for a down payment on a new aircraft carrier? And, really, do we need to buy new nuclear weapons, or "improve" the existing ones, at a cost of $100 billion over the next 10 years? (President Obama signed on to this sum, in part, as a deal to get the Senate to ratify the New START treaty with the Russians, but c'mon. The treaty allows the United States and Russia to retain 1,550 long-range nuclear warheads. Who cares to make the case that letting the arsenal rot to 500, or 200, would endanger national security?)
The fact is, not all social programs really help people in need—and not all defense programs really help the national defense. Many of them stem from institutional imperatives (for example, the fact that, until recently, the Air Force was run by fighter pilots), contractor games-playing (for example, the tendency for weapons manufacturers to spread subcontracts to as many congressional districts as possible, the better to build constituencies), and bureaucratic politics (the mutual back-scratching game, which has been going on since the mid-'60s, of divvying up the defense budget among the Army, Navy, and Air Force, in almost precisely even proportions).
Probably not much can be done to alter these basic facts without throwing the entire Pentagon, Congress, and defense-contracting world into utter chaos—and thus causing way more trouble than it's worth. (Disrupting the even divvying of the defense budget, for example, would almost certainly reignite the interservice wars—and they were wars in every sense but the shooting—that dominated military politics throughout the 1950s.)
But if these realities can't be changed, they should at least be recognized—in order to grasp the underlying fact that the Defense Department is as much a bureaucracy as any other federal agency, and thus to demystify the incantation that Program X, Y, or Z, or Mission Q, R, or T, can't be slashed or killed without doing grievous harm to "national security." Maybe the claim is true; but it's time to start setting priorities and asking for proof.