um, they already have figured out how. they know all they have to do is keep killing Americans and drag this war out and the American people forget quickly and wont want the military to stay. look at vietnam. they knew they couldnt go head to head, all they had to do was play the political time game.
Just to back you up a bit:
"You can kill ten of my men for every one I kill of yours, but even at those odds, you will lose and I will win." - Ho Chi Minh