By the 20th century, war ceased to be an encounter between two armies. It became an encounter between two societies, because a factory worker producing a gun or a bomb is as deadly as a pilot.

Now if you can recognize and memorize a grandmaster's game, and you have the respect to understand [Zimbabwean president Robert] Mugabe who has survived past anyone's expectations, and make the simple assumption it wasn't an accident, and you understand why he did what he did, now you're ready to predict ... The key to forecasting is to understand both the constraints nations are under and the manner in which the struggle for power shapes leaders.

Idealism is frequently another word for self-righteousness, a disease that can only be corrected by a profound understanding power in its complete sense.

There has never been a century that has not had a systemic war - a systemic war, meaning when the entire system convulses. From the Seven Years' War in Europe to the Napoleonic Wars of the 19th century to the World Wars, every century has one.

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're young and going to war, it's a genuinely exciting moment. You are going to risk yourself. On the battlefield, you are suddenly free. You realize: I'm here, I'm in it. Exaltation. Suddenly you're hit by another extraordinary feeling: my God, I can be killed. And: will I embarrass myself? It's like you're in a kaleidoscope and all of these extraordinary feelings are zipping by.

War to me is very much like sex. You can develop a theory that says sex is primarily for the exchange of genetic material, or that it's a celebration of life, or you can make up 50,000 theories about why human beings have sex, all of which are in some sense true, all of which by themselves miss the point. Because the answer is extraordinarily complex. It may be for fun, it may be for reproduction, for financial reasons, any number of things.