Recent events have raised questions about the extent to which military intervention promotes democracy and the degree to which this depends on the nature of the intervener+ We argue that traction on these issues is best obtained by focusing on the policies of the target state that have the greatest implications for the political survival of the intervening state's leader and the kind of governmental institutions in the target state that are most likely to produce them+ This perspective generallyäóî although not alwaysäóîpredicts that third-party military intervention in civil wars, other intra-or interstate disputes and wars will lead to little if any improvement, and all too often erosion in the trajectory of democratic development+ Three hypotheses on the impact of third-party intervention by democracies, autocracies, and the United Nations are then tested and strongly supported against a counterfactual expectation of what the democratic trajectory would have been in the absence of intervention+ The U+S+ invasion of Iraq has rekindled debate about the impact of military inter-vention on democratic nation-building and, particularly, the extent to which it depends on the character of the intervener+ Some leaders, such as French Presi-dent Jacques Chirac, have argued that military intervention and democracy build-ing is best advanced in states such as Kosovo when it is carried out by a broad multilateral coalition of democraticäóîin this case Europeanäóîstates+ Others, such as U+S+ President George W+ Bush, have implicitly dismissed the necessity of a broad-based coalition and stress the importance of the unity of command that can often be most effectively achieved by a single democratic state acting alone or in concert with a small coalition+ Leaders from the developing world and those closely identified with international institutions, such as Kofi Annan, the secretary general of the United Nations {\~{}}UN!, argue that the greater legitimacy that the UN pos-We benefited greatly from the wise counsel of Feryal Cherif, Michael Gilligan, Shanker Satyanath, and Alastair Smith, each of whom read or discussed in depth earlier versions of this study+ Patrick Regan was also extremely helpful in providing data and guidance in the use of the data on interven-tions that he has made available+ The study was significantly improved by the insightful advice of the anonymous reviewers {\~{}}we wish we could thank them by name! and by Lisa Martin's able and thought-ful guidance+ Authors often complain about referees; we have nothing but praise for the contributions they made+ Of course, we alone are responsible for any errors and for all remaining shortcomings in this investigation+