When genocidal violence exploded in Rwanda in May 1994, the United States sounded a particularly strident, even obstructionist, voice of caution against intervention by any outside forces to stop the atrocities. Although the United Nations Assistance Mission in Rwanda (UNAMIR) already had a small contingent on the ground at the time of the crisis, the United States quickly moved to oppose an expanded UN presence.

As events unfolded in Rwanda, American policy makers were strongly influenced by the specter of the Somalia "disaster" of less than a year earlier as they deliberated possible options. In December 1992 American forces entered Somalia as part of a UN mission to feed starving people in a nation wracked by internal chaos. With CNN broadcasting images of the soldiers coming ashore to rescue the at-risk population, this gesture of international goodwill seemed destined for success. Over the next year the mission expanded from...