State emergence is an essential dynamic of the international system, yet international relations scholars pay it little attention. Their oversight is all the more unfortunate because international politics ultimately determine which aspiring system members will succeed in becoming new states. Existing models of state emergence rely exclusively on internal or domestic-level explanations. However, the international system is inherently social; therefore any aspiring state's membership also depends on the acceptance of its peers. I present a novel, international-level model of state birth that suggests state leaders should use decisions regarding new members strategically to advance their own interests, not passively abide by domestic factors. I test this argument using a new data set on secessionism and Great Power recognition (1931–2000). I find that external politics have important, underappreciated effects on state emergence. Furthermore, acknowledging the politics of recognition's centrality to state birth alters our understanding of civil conflict dynamics and conflict resolution and suggests important implications for system-wide stability.