Economic coercion depends on the credibility of both threats to punish noncompliance and assurances that compliance will not be punished. What instruments can states deploy to make the necessary assurances without undermining the credibility of their threats? This article describes how some actions that bolster the credibility of threats can simultaneously undermine the credibility of assurances. It then argues that states can mitigate the challenge by carefully selecting coalition partners with different interests who can hold them accountable. The paper applies the theory to the Iran deal negotiation and finds that Congressional resolve to maintain sanctions initially stymied progress. The United States was ultimately able to increase the believability of its commitments by partnering with European states that were more open to removing sanctions.

We argue that the gunpowder revolution in medieval Europe encouraged the amal- gamation of smaller polities into larger centralized states. The advance in military technology made existing fortifications obsolete and substantially raised the cost of defensive investments. Small polities lacked the fiscal capacity to make these invest- ments, so they had either to ally or merge with others. Alliances created prospects of free-riding by interior cities on border cities. In contrast, centralized, territorial states benefited from geographic and fiscal economies of scale, facilitating defensive invest- ments at the border that protected the interior while limiting free-riding and resource misallocation. Using a new dataset on fortifications in 6,000 European cities, we find that states made defensive investments in areas of territorial contestation, closer to borders, and farther from raw building materials. These findings are consistent with our theory that large centralized states arose in part as a consequence of changes in military technology.

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