Foreign powers can’t win guerrilla wars.

"War with Iran—a war that would unleash an apocalyptic scenario in the Middle East—is probable by the end of the Bush administration. "
[snip]
“As a people we are enormously forgetful,” Dr. Polk, one of the country’s leading scholars on the Middle East, told an Oct. 13 gathering of the Foreign Policy Association in New York. “We should have learned from history that foreign powers can’t win guerrilla wars. The British learned this from our ancestors in the American Revolution and re-learned it in Ireland. Napoleon learned it in Spain. The Germans learned it in Yugoslavia. We should have learned it in Vietnam and the Russians learned it in Afghanistan and are learning it all over again in Chechnya and we are learning it, of course, in Iraq. Guerrilla wars are almost unwinnable. As a people we are also very vain. Our way of life is the only way. We should have learned that the rich and powerful can’t always succeed against the poor and less powerful.”