Bargaining theories of war emphasize private information as a cause of conflict. Leaders are uncertain about one another’s military strength, preferences, and trustworthiness which may lead to the outbreak of conflict. Thus, a critical step in the onset of conflict is determining what leaders know and where they get their information from. I argue that what state leaders know is shaped by their embeddedness in the network of diplomatic relations among nations. Ties in the diplomatic relations network can serve as an infrastructure for information exchange and as a costly signaling device. Leaders may communicate with other leaders to obtain strategic information about potential opponents. They may also use the overall pattern of their diplomatic interactions to disseminate and receive costly signals about their preferences and demonstrate trustworthiness and alliances. Using data on diplomatic relations from 1990 to 2010 and methods of network analysis, I show that states’ positions in the diplomatic network are a powerful predictor of the onset of international conflict.