I build a static, complete information, three-player bargaining model of war. Without dynamics or incomplete information, war is always avoided. However, the threat of war determines the nature of alliances. The model uses a notion of cooperative stability to predict balancing and bandwagoning behavior in alliance formation. Given the assumptions of the model, a stable state always exists. Stronger allies increase the potential for war threats against a non-allied player. However, stronger allies also demand larger shares of an alliance's total payoff. Balancing (bandwagoning) alliances form when the within alliance utility of a player is uniformly decreasing (increasing) in the resources of an alliance partner.