Ron Paul foreign policy

I realized that I am, in fact, a Libertarian a few years ago. But there is one thing I do not understand about Libertarianism: Why are Libertarians, like Ron Paul, against a strong foreign policy? Doesn't an iron fist ensure that American liberties are preserved?

In other words, convince me that Ron Paul's foreign policy views are better than those of other conservatives. How will the US continue to be an economic and military powerhouse who foreign powers know not to mess with if we pull troops out of every nation?