Listening for That Whistle

For U.S. Marines, days of routine laced with danger

Around the runways of Beirut's international airport, the low, sandbagged bunkers form ragged lines, cluttering a 2½-sq.-mi. stretch of barren, unprotected ground. On two sides the old airport fence topped with barbed wire divides the encampment from the predominantly Shi'ite shantytown of Hay es Sullum, where bombed-out buildings sometimes shelter Muslim fighters armed with mortars and rocket-propelled grenades. In the surrounding hills that rise 3,000 ft. from the plain, Druze and Christian militias clash, igniting the night skies with tracer rounds and exploding shells.

For the estimated 175 U.S. Marines of Alpha Company, 1st...