IT'S ALWAYS DIFFICULT to know whether a war -not just Iraq, but any other war- has been worth it, writes Robert Kagan:

Serious scholars still debate whether the Civil War was necessary, never mind the more obvious "wars of choice" such as World War I, the War of 1812, the Spanish-American War, the Korean War, wars in Vietnam and Kosovo, and the Persian Gulf War. To a certain brand of American isolationist, even World War II was unnecessary and counterproductive. So there is nothing remarkable about polls showing Americans wondering whether the recent Iraq war was "worth it." It is a great American myth, voiced by John Kerry last year, that the nation goes to war only when there is no question about the necessity of going to war. There's always a question. Even if the Iraqi insurgency disappeared tomorrow, George Ibrahim al Washington became president of Iraq and every liter of Saddam Hussein's onetime stockpile of chemical and biological weapons suddenly appeared in the desert, historians would still spend the next century debating whether the war was "worth it."

Wars remain subjects of debate not just because their "necessity" is in doubt but also because their results are mixed. No war has produced unmitigated successes. The Civil War did not completely "free" African Americans, who remained oppressed for another century. World War I destroyed Europe, and helped pave the way for the rise of Hitler and the Soviet Union. World War II defeated Hitler but enslaved half of Europe behind the Iron Curtain and introduced the world to nuclear warfare. The Persian Gulf War drove Hussein out of Kuwait but helped produce the Osama bin Laden we know today. Add to that the millions of innocent lives lost, and the toll of these wars, generally regarded as "successful," is high. Does that mean those wars were not "worth it"? Demanding unmixed results and guarantees against the unintended consequences of war is as unrealistic as demanding absolute confidence in the "necessity" of going to war in the first place.

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