Open Secrets explores the causes and consequences of secrecy in proxy alliances. It presents a novel theory to explain why states sometimes successfully manage proxy allies, while other times struggle to influence their behavior. The book offers a more nuanced picture than two common, but opposing, views: that proxy warfare is either a dangerous gamble for states unlikely to yield strategic benefits, or that it presents a cheap, fast, and easy way to achieve foreign policy goals. Instead, Open Secrets shows how plausible deniability is a key variable that shapes how states influence the behavior of proxy groups.The degree of secrecy in a proxy alliance is a deliberate choice. It stems from the calculations leaders make about what information to keep secret, and from whom—especially critical domestic constituencies. When those constituencies are dovish, leaders form "perfect secret" proxy alliances. Conversely, when they are more hawkish, leaders form "open secret" proxy alliances. Yet, open secrets are more dangerous for states. They create opportunities for proxy groups to exploit domestic political dynamics to their advantage, significantly complicating a state's influence over the proxy group.Open Secrets draws on a wealth of historical and primacy source material to illustrate the dynamics of secrecy in proxy alliances across a range of case studies, from U.S. Cold War proxy alliances to Indian and Syrian regional proxy relationships. It also explores patterns of proxy alliances in the contemporary environment, demonstrating how systemic changes in technology are shaping the secrets states are able to keep and the changing character of proxy alliances. This book weaves together the literature on covert action, secrecy, proxy warfare, and alliance politics to shed new light on an enduring aspect of international politics.