Network Context and the Effectiveness of International Agreements

Abstract Why do some international agreements yield more cooperation than others? I argue that the network context of agreements conditions their effectiveness. I focus on bilateral defense cooperation agreements (DCAs), which promote defense activities like joint military exercises, peacekeeping, arms trade, and the sharing of classified information. Because DCAs emphasize ongoing cooperative actions, they offer an ideal setting to assess treaty effectiveness. The analysis shows that when agreements are embedded in transitive “friend of friend” relations, characterized by extensive ties to common third parties, they generate higher levels of cooperation. I argue that this network effect is the result of policy convergence. When states share ties with common third parties, their own policies become more closely aligned, and this alignment in turn reduces the costs and increases the benefits of cooperative actions. The theory and findings developed here apply to a wide array of cooperative interactions across multiple issue areas. The effectiveness of international agreements depends on network context.