Why do great powers intervene in some revolutionary civil wars, but not in others? When they do intervene, how do they choose sides? Why are some great powers more active in such struggles? Finally, how do intervening great powers choose sides — sometimes siding with the embattled government and other times the armed opposition? Although they have long acted as kingmakers in armed revolutions, we still know relatively little about how and why the world’s leading powers intervene where they do. This project aims to answer these questions by developing new theory and providing global systematic empirical evidence to further our collective understanding of this fundamental political phenomenon that has continued to shape the contours of world politics.