When the Washington Times announced that libertarianism is trendy, I couldn’t help but think “It would be a lot trendier if libertarians had been against the Iraq War from the start.”

Plenty of libertarians were against it, of course. But if you remember how integral isolationist/ non-interventionist foreign policy was to the libertarian idea back in the ’70s and ’80s, the libertarian reaction to the Iraq War (and the War on Terror generally) has been quite astonishing.

You might say that libertarians changed their mind because Islamic fundamentalism is such a serious threat. But it’s a lot less serious than the Soviet threat. And back when the Soviets still ruled eastern Europe, the standard libertarian foreign policy prescription was to pull out of NATO, Korea, and Japan. Similarly, you might say that Islamic fundamentalism is so ideologically repugnant to libertarians that they were willing to make an exception. But from a libertarian perspective, Marxism-Leninism is even worse, isn’t it?

So why did libertarian thinking on foreign policy change so sharply? Here are a few possibilities:

1. Libertarian commitment to non-interventionism was always much weaker than it appeared. Rothbardians (and ex-Rothbardians who didn’t want to seem like sell-outs) had key positions in the Libertarian Party, think tanks, etc., and falsely claimed to speak for all libertarians. In fact, many libertarians held the diametrically opposed Rand/Goldwater view that the U.S. should take off the kid gloves and start “really” fighting the Soviets.

2. The movement away from natural rights and toward consequentialism made libertarians more open to using government for good causes. Indeed, the very fact that Islamic fundamentalism is a lot weaker than the USSR makes it a more attractive target.

3. The movement away from philosophy and toward economics made libertarians vulnerable to the simple-minded view that “getting tough” is a free lunch.

4. The rise of the “Establishment libertarian” led to moderation. In the 70’s and 80’s, libertarianism was an alienated outsider movement. Over time, however, many libertarian thinkers have been accepted into polite intellectual society. The cost is that they had to distance themselves from “impolite” positions.

5. The end of the Cold War revived the libertarian/conservative alliance, making libertarians more receptive to conservative positions on everything from foreign policy to immigration.

What do you think? Anyone got a better explanation? To repeat, the question is not whether the war was actually a good idea, but why so many libertarians supported it.

Update: Alex Tabarrok suggests a much simpler story: Terrorists launched a successful attack on American soil; the Soviets never did. What do you think?