Instances of external state involvement in seven postwar secessionist movements—those of Katanga, Biafra, the Southern Sudan, Bangladesh, Iraqi Kurdistan, Eritrea, and the Moro region of the Philippines—were analyzed to shed light on the patterns of interaction between the international system and secessionist minorities. Examined and tested were numerous assumptions of conventional wisdom on the subject, as well as a variety of other relevant questions concerning the constraints on, content of, and reasons for involvement. The results were contrary to many of the common assumptions. For example, given the international regime's norm against involvement with groups that threaten territorial integrity, external state support of these groups was more extensive than would be expected; and support was given for diverse reasons, rather than based solely on the prospects for tangible gain. Additional results of this study suggest a series of hypotheses for further examination.