The Defense Department looks to be the odd man out in the post-debt-ceiling-deal celebrations (if this quiet, gray day in DC can be characterized as, in any way, “celebratory”). Gary Schmitt and Thomas Donnelly at The Weekly Standard explain:

The so-called “second tranche” of deficit reduction, in the hands of a soon-to-be-named “supercommittee” of lawmakers backed by the threat of an automatic sequestration “trigger” should it fail to agree on sufficient further cuts, would almost certainly push the military past what incoming chairman of the Joint Chiefs Gen. Martin Dempsey described as a “very high risk” threshold of cuts. The deficit reduction law seeks another $1.2 to $1.5 trillion in cuts and, if the supercommittee fails to meet the target, mandates additional reductions (split between domestic and security accounts).

The composition of the supercommittee matters a lot. It’s likely that there will be great solidarity among the Democratic members; they will be looking to defend social entitlements (and also looking to frame the 2012 election as a Republicans-throw-granny-under-the-bus contest). If they can’t raise taxes, they’ll look for bigger defense cuts. Conversely, the prime directive for Republicans will be no new taxes. They’d love to run on that issue in 2012. Unless they’re also hawkish on defense, the military will be the odd man out on the conservative side, too. And the sequestration, while allowing both sides to point fingers at one another, would also rip another $500-billion-plus out of defense spending.

Defense Secretary Leon Panetta appears to be all too well aware of this reality. Just one day after the deal, he immediately sent a message to Pentagon rank-and-file and to Congress to warn about the coming cuts — and to promise that he will do everything in his power “to ensure that further reductions in defense spending are not pursued in a hasty, ill-conceived way that would undermine the military’s ability to protect America and its vital interests around the globe.”

The Wall Street Journal Washington Wire reports:

In particular, Mr. Panetta expressed worry about the automatic cuts that would result from a failure of the special congressional panel. “If that happens, it could trigger a round of dangerous across-the-board defense cuts that would do real damage to our security, our troops and their families, and our ability to protect the nation,” he said.

That scenario, Mr. Panetta added, “would be completely unacceptable.”

As Panetta points out in his message, that “potential deep cut in defense spending is not meant as policy. Rather, it is designed to be unpalatable to spur responsible, balanced deficit reduction and avoid misguided cuts to our security.”

But is it unpalatable enough? When I first heard about the trigger mechanism, it sounded OK (never stellar, but maybe suitable) — cuts to domestic spending to galvanize Medicare-minded liberals, cuts to defense spending to galvanize security-minded conservatives. But I’m increasingly worried, especially in light of the facts. Consider: In 2010, the defense budget was just $712 billion. Compare that to the unfunded liability of Medicare: $30.8 trillion. Because domestic spending is proportionally larger than defense spending, equivalent cuts will disproportionately hurt defense (and don’t buy the business about cuts to “security” rather than “defense” — the Defense Department will bear the brunt).

That means, however much Democrats on the Super Committee might rail against the automatic cuts to domestic spending that would result from the committee’s failure, they would probably stomach those cuts rather than agree to another deal without tax hikes. Schmitt and Donnelly sound optimistic that Republicans will stand firm on taxes — but to stand firm on taxes, they’ll have to be willing to sacrifice defense. I’m optimistic Republicans will defend defense funding — but that means they’ll have to sacrifice taxes. (Of course, debate still exists as to whether the Super Committee can even raise taxes in the first place, but it seems pretty safe to say Obama, at least, thinks the Committee can take a “balanced approach.”) In other words, Republicans will have to cave on tax hikes or the Committee will result in deadlock (and consequent cuts).

But here’s why Republicans should remain steadfast and why the Committee shouldn’t deadlock: The facts clearly demonstrate that entitlement spending is the problem. Just as all the talk of “revenues” distracts from the basic truth that we have a spending problem, so all the talk about “defense spending” distracts from the basic truth that we have an entitlement problem. As this chart from The Heritage Foundation shows, completely eliminating defense spending still wouldn’t solve the country’s fiscal issues:

Republicans on the Super Committee better remember that. As everybody keeps saying, the Committee composition will be crucial: We’ll need deficit and defense hawks.