To Americans, the lesson of World War II was that, to prevent a repetition, the United States had to promote global stability. It had to accept short-term costs and burdens to avoid larger long-term costs and burdens. But the triumphalism following the Cold War fed overconfidence. Pax Americana would continue forever. It was "the end of history'' -- democracy and free markets would spread. The United States was a "hyperpower.''

The flaw in all this theorizing was to mistake strength for power. Statistically, the United States remains the world's strongest nation. Its economy is the wealthiest, triple the size of Japan's. Its all-volunteer military is the best trained and most technologically advanced. "No other state is building nuclear-powered aircraft carriers, stealth fighters or unmanned aerial vehicles,'' writes Max Boot, author of "War Made New.''

The trouble is that strength -- measurable and impressive -- does not translate directly into power. Power is the ability to get others to do what you want. Here, America is weaker.