The author examines the bases of American military participation in the array of Third World activities falling under the general rubric of peacekeeping and peace-enforcement. The relevance of this inquiry was underscored by President Clinton in his Inaugural Address, when he added situations where "the will and conscience of the international community are defied" to traditional vital interests and as times when American military force might be employed. He considers the major instances in the post-cold war world where so-called humanitarian interventions have occurred or may occur: the aftermath of the Persian Gulf War, Somalia, and Bosnia and Herzegovina. The author then examines the effects of these actions on the principle of sovereignty. He next turns to the emerging roles of peacekeeping and peace-enforcement and the conceptual and practical differences between them, and concludes with some cautionary lessons for the Army.