Constraint theory asks: What is the price for doing this? Now one way around constraint theory is declaring your enemy crazy. Crazy and stupid are not concepts used in forecasting. When people say they're really stupid or they're crazy, that's laziness. That means I don't want to think through their position or about what they're really going to do.

Success looks like you sitting here pretty confident that an armed brigade isn't going to come pouring in here and blow your head off. Which I don't think is your major concern. Therefore, the United States' foreign policy is successful.

When I went to war, I did not go making geopolitical calculations. I went to war with a lust.

The important thing in war is that there is an element of rage, but you must remain very distant from it.

Recent presidents have gone off on ad hoc adventures. They have set unattainable goal because they have framed the issue incorrectly, as they believed their own rhetoric.

When you have the countries like Germany, China, and Russia decline, and be replaced by others, that's when systemic wars start. That's when it gets dangerous, because they haven't yet reached a balance. So Germany united in 1871 and all hell broke loose. Japan rose in the early 20th century, and then you had chaos. So we're looking at a systemic shift. Be ready for war.

Constraint theory argues a number of things. First, that the impossible has to be identified. Second, that the actor is then constrained by circumstances to act a certain way. For example, should we invade ISIS? Can we invade ISIS? What would it take to invade ISIS? Once you ask that question you discover the price of that option and then you take a look at American politics and see that the country is probably not prepared to invest the 2 to 3 million people that it would take to defeat ISIS and the insurgency afterwards. All right, so that's not going to happen.