Moments after midnight, 300 Viet Cong guerrillas crept through sugarcane fields toward a camp of U.S. and South Vietnamese Special Forces at Hiephoa, barely 20 miles west of Saigon. Ducking under watchtowers bristling with machine guns and floodlights, the Reds knifed a sentry, forded a three-foot-deep moat, snipped three barbed-wire fences, and slipped into the compound—evidently in collusion with a spy inside, who unlocked the gate. Then, while guerrillas outside opened up with a mortar barrage, the infiltrators attacked to the blast of a bugle.
Running from barracks to barracks, they killed 37 South...