WASHINGTON -- American troops have arrived in Liberia after Liberian President Charles Taylor fled into exile. Whether these peacekeepers, and the larger African contingents to come, will bring peace in the three-sided civil war is yet uncertain. What is certain, however, is that reconstructing Liberia is not America's responsibility.

The world is full of tragedy. As many as 4.7 million people have died in five years of war in Congo. A brutal communist insurgency burns in Nepal. In Colombia, the military, communist insurgents and rightwing militias battle. A score of other nations, such as Liberia, endure instability, ethnic strife and genocide.

America could stop some fighting and save some lives. But it can't -- and shouldn't try to -- do everything. The U.S. is better than any other state at fighting wars. It possesses the world's finest military. America could defeat any other power or combination of powers. Which means Washington's most important international role is to prevent a hostile hegemonic power from dominating the Asian or European continents.