I have a buddy in the Royal Marines and he says apart from the Talibans in Afghanistan, the British/American camp often gets invaded by these little shits:
Also, he was telling me about the Sniper Training course he took to get a promotion. Basically, you have three days to sneak up on your target. Your target is just a dude with binoculars in a lookout spot trying to find you. If he spots you, it's over. Everything has to be done really slowly.