This study examines how military counterterrorism (CT) measures affect the quality of democracy by altering civil–military relations (CMR) and focuses on CMR as the main causal mechanism. We argue that the use of military measures in CT jeopardizes democracy at the societal level by increasing the belief that only the military is equipped to deal with the threat at hand. Therefore, erosions of civil liberties are tolerated in exchange for security. Second, we argue that military CT measures change the balance between the military and civilian executive powers in procedural and liberal democracies. While the military’s executive power increases in procedural democracies, civilian executive power increases and goes unchecked in liberal ones. Case studies of the United States and Turkey show that military CT measures affect CMR in these countries, which generate a similar tradeoff between security and the quality of democracy, albeit via different causal mechanisms. While that tradeoff is less severe in the United States, Turkey is more vulnerable to erosion of democracy.