The Pentagon says it can handle the $325 billion in cuts that will be required during the next decade as part of the deal that ended the debt-ceiling crisis. But not a penny more.

The deal created a so-called supercommittee composed of six Democrats and six Republicans, all members of Congress, who are charged with coming up with $1.5 trillion in additional reductions by late November, balanced between defense and domestic spending. If they fail, the budget would be cut automatically, with at least $500 billion in reductions from the Defense Department.

This proviso is the only significant concession that President Obama got in the deal, in exchange for giving up on any tax increase -- and practically everything else. It is supposed to create special pressure on Republicans in the forthcoming negotiations, as Republicans are thought (not without reason) to be fond of defense spending. But the Pentagon, now led by former CIA Director Leon Panetta, says that cuts of this magnitude would threaten our security, harm our troops and their families, and so on.

We aren’t especially fond of defense spending. In particular, we have no idea whether the warnings by Panetta about the terrible dangers of larger cuts are accurate, or just blowing smoke as part of the usual budget game. But we do know that making the size of the Pentagon’s budget dependent on factors that have nothing to do with national security -- such as the ability of Republicans and Democrats to get along on a supercommittee -- is an odd way to go about things. And we know that Panetta’s position -- $325 billion, OK; $326 billion, disastrous -- isn’t as absurd as it sounds.

Spending on national security is different from other government spending. If you have a program like the National Endowment for the Arts, for instance, it makes perfect sense to say, “This is something good for our nation, and we should have as much of it as we can afford. In good times we should spend more on it, and in bad times we should spend less.” Other programs, like those that subsidize weatherization of low-income housing, should be more resistant to cuts, but their budgets ultimately will have to be affected to some extent by the state of the economy and the government’s pocketbook.

In the case of national security spending, even minimal flexibility makes little sense. We should spend every dollar needed to make us secure, and not a penny more. Obviously we can’t know in advance what that exact number is. We can argue about it. And we can assume that the Defense Department will exaggerate it. But we should try to compute it as best we can, and then apply it. It should not be part of hostage negotiations over the federal budget.

If there is really an additional $500 billion that can be squeezed out of Defense without leaving us inadequately protected, we should go ahead and squeeze now. If taking even $1 billion -- let alone $500 billion -- out of the Defense budget will do real damage to national security, then the Pentagon should be exempt from further cuts.

The one arrangement that makes no sense is a national security budget contingent on political battles that have nothing to do with national security.

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