As an episode in Soviet-American global competition, the conflict in Nicaragua has served to illuminate a recurring problem in American governance: the difficulty of getting Capitol Hill and the White House together on a coherent U.S. foreign policy. Since the Vietnam debacle, the zigzags in U.S. policy overseas have intensified. The War Powers Act (1973) and Congress's initial refusal to fund anti-Communist guerrillas in Angola (1976) were just two early symptoms of the same distrust that led...