It was as if the five years of almost ceaseless firefights and ambushes had been a misunderstanding -- a tragic, bloody misunderstanding. More than 40 U.S. soldiers have been killed, and scores more wounded, in helicopter crashes, machine-gun attacks and grenade blasts in the Korengal Valley, a jagged sliver just six miles deep and a half-mile wide. The Afghan death toll has been far higher, making the Korengal some of the bloodiest ground in all of Afghanistan, according to U.S. and Afghan officials.