Why did Egypt’s democratic transition fall to a military coup in 2013? While most accounts highlight popular disillusionment with the Muslim Brotherhood’s rule, this paper instead reveals the military’s interests in staging a coup. It argues that the Brotherhood's Mohamed Morsi had contested several of the military’s corporate interests, including its constitutional prerogatives, monopoly over national security decision-making, economic empire, and largely secular identity. Drawing on a survey of 2000 Egyptian military personnel, this paper shows that each of these encroachments on the military’s interests bred support for the 2013 coup. The second half of the paper then turns to explaining why Morsi would pursue a confrontational course with the military. Based on interviews with exiled members of the Brotherhood, it finds that Morsi faced both electoral and normative incentives to reign in the military’s power, but ultimately miscalculated the extent to which he could do so, sparking a coup. Overall, the experience highlights the difficulties and uncertainties that plague democratic transitions with powerful militaries.