President Trump’s remarks about Iran on Wednesday weren’t exactly a model of clarity. The president clearly wanted to project toughness (“As long as I’m president of the United States, Iran will never be allowed to have a nuclear weapon”) while continuing to position himself as the president who was getting us out of Middle Eastern entanglements. (“The fact that we have this great military and equipment, however, does not mean we have to use it. We do not want to use it. American strength, both military and economic, is the best deterrent.”)

There’s a potential contradiction here, of course: What if deterrence doesn’t work? Does Trump really think that after one targeted killing, we can rest assured that Iran will now be too overawed by our military musculature to even think about pursuing a nuclear weapon?

He couldn’t possibly. What he did was imply that a third party might fill the gap, with a promise to get NATO more closely involved. This seemed an odd stance for a president who keeps complaining that the rest of NATO underfunds their militaries — how are we more likely to succeed by dragging the cut-rate second-stringers into the act? But presumably that wasn’t really the point; the point was Trump’s long-standing obsession with getting NATO to pay their “fair share,” in blood and treasure, for maintaining the alliance.

He’s right, of course; NATO is essentially free riding on U.S. military might. Americans used to rather glory in the U.S. military’s outsize prowess, but as budgets have tightened and the foreign wars have dragged on, many have come to resent it. They’d like beefier European militaries to assume the burden of the European security umbrella, not to mention policing the less stable bits of the world.

It isn’t an unreasonable desire. But that doesn’t mean it’s an achievable one. And it certainly won’t happen within the Trump presidency, because developing military prowess, like developing any organizational competency, takes time as well as money. And when it comes to a nation’s military, you can’t take the usual executive shortcut of hiring outside expertise.

If you want your military leaders to be patriotic citizens rather than mercenaries, then you need to grow them internally. This means either starting them young and training them for many years — at some risk of discovering, once you get into a real war, that many of them can’t hack it. Or you can take a shortcut by tossing a substantial chunk of your population into a hot war and finding out who’s actually good at it — a bloody and unpleasant way to build your military, which is why few nations choose it except under maximum duress.

That was always the fatal flaw in the naive Trumpian idea of forcing Europe to take up our slack simply by threatening to withdraw from NATO. Europe can’t build up the necessary military capacity in the space of one administration, so if we abruptly stop enforcing Pax Americana, plenty of NATO members may well simply decide that they’ll have to cozy up with Russia or China, or regional powers such as Iran, paying them off to protect European interests.

Pushing U.S. allies into the strategic orbit of those other powers would, in turn, make it harder for the United States to advance its own interests, like wringing fairer trade terms out of China. It would also, in the short term, mean a lot more conflict in places like the Middle East.

Of course, as Trump noted in his speech, the United States’ newfound energy independence leaves us less vulnerable to such conflicts. Yet we still have plenty of reasons to fear them. For one thing, a regional war in the Middle East would be very dangerous for Israel, Trump’s favorite ally. For another, it would send the global price of oil rocketing, which is good for oil producers but bad for oil consumers — and despite the shale oil boom, America still has a lot more of the latter than the former.

A charitable defense of Trump’s suggestion is that he’s already realized that his promises of big NATO reform won’t materialize, but is hoping that voters haven’t. That’s a reasonable assumption, since voters usually don’t follow foreign policy closely. An even more hopeful interpretation is that the events of the past few days drove home the risks of chest-thumping escalation, after which Trump very sensibly sought a face-saving implausibility rather than ramping up the aggression until the United States, rather than Europe, found itself in yet another hot war.

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