A strategic passage wanted by the Taliban and al-Qaeda, Afghanistan’s Korengal Valley is among the deadliest pieces of terrain in the world for U.S. forces. One platoon is considered the tip of the American spear. Its men spend their days in a surreal combination of backbreaking labor—building outposts on rocky ridges—and deadly firefights, while they try to avoid the mistakes the Russians made. Sebastian Junger and photographer Tim Hetherington join the platoon’s painfully slow advance, as its soldiers laugh, swear, and run for cover, never knowing which of them won’t make it home.