Great wars can only be fought by great powers.

While analogies are useful, however, they can also be misleading. They smuggle in assumptions that can be wrong.

Certainly, protecting oppressed people, stopping ethnic conflict and promoting responsible governance are worthy goals. But none is as important for American security and prosperity as keeping the peace in the Middle East, Europe and East Asia.

To call the American role in the world imperial was, for many who did so, a way of asserting that the United States was misusing its power beyond its borders and, in so doing, subverting its founding political principles within them.

One thing worse than an America that is too strong, the world will learn, is an America that is too weak.

American power confers benefits on most inhabitants of the planet, even on many who dislike it and some who actively oppose it, because the United States plays a major, constructive, and historically unprecedented role in the world.

The real threat to world stability is not too much American power. It is too little American power.