Sometimes, Right Makes Might

THROUGHOUT HISTORY, GOING BACK AT LEAST TO THE Peloponnesian War, nations have ascribed idealistic purposes to their military struggles. But as with Sparta's classic balance-of-power contest with Athens, discernible national interests have always been at stake. What makes America's intervention into Somalia seem so inspiring -- and also so dangerously slippery -- is that it may be the first time since the Crusades an invasion has been launched for a purely moral rationale.

A logical place to look for a modern precedent would be the days of Woodrow Wilson, that professor of Presbyterian rectitude who draped foreign policy with a mantle...