While it is never wise to underestimate an enemy, it's not good to overestimate him either. The youthful populations of Muslim nations are huge... why aren't they in a real army, instead of the few in these covert ragtags? Why does Saddam and the Sauds need to pay Palestinians to kill themselves? They have the means to join and make an army worthy of the name.
Killers, assassins--but they don't look very warrior-like to me.
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Looking like a warrior is irrelevant. This isn't the movies. They are using the same methods Mao used to conquer China and the communists used to conquer Russia and Viet Nam. Infiltrate. Terrorize. Wear down. Get concessions. It's working.