How do coalition partners affect the dynamics of crisis bargaining? I analyze a model in which a potential coalition leader faces a trade-off between signaling resolve to a target and retaining a partner's support by limiting the costs of war. The strength of the target conditions the partner's effect. When the target is strong, the need to ensure military cooperation reduces the probability of war by discouraging bluffing, though resolute types can signal resolve by foregoing coalitional support. When the target is weaker, a resolute coalition leader moderates threats to preserve military cooperation, foregoing the chance to signal resolve and increasing the chances of war, even as the partner successfully moderates the leader's bargaining posture. Thus, coalitions may face higher probabilities of war against weaker targets than stronger ones, coalitions are more likely against weak than strong targets, and partners can increase or decrease the probability of war.