KORANGAL VALLEY, Afghanistan - At night, the mountains glow from artillery strikes. By day, gunbattles echo down the valley. Five years after the Sept. 11 attack, Americans are battling al-Qaida militants in this remote area where the U.S. military says the group hatched the terror plot. Only about 100 hard-core Afghan, Arab and Pakistani insurgents operate in the Korangal Valley, but this is where the U.S. last year suffered its worst combat loss in Afghanistan and where the military believes at least second-tier al-Qaida leaders still hide and plan attacks. Many of the U.S. soldiers here see their offensive as...