Since the attacks of 11 September 2001, there has been a sharp increase in attacks by Islamist terrorists. Analysts have posited a number of causes behind terrorism’s global intensification, including poverty, failed states, and political unrest. One explanation, however, stands out as being uniquely important: a country’s level of freedom. Freedom combats Islamist terrorism in two broad ways. First, it strikes at the root of Islamist extremism, making it more difficult for terrorists to credibly claim that their faith is under attack. Second, freedom is an effective weapon of counterterrorism. The recognition that freedom naturally combats terrorism suggests that countries around the world have national-security interests in reversing decades of democratic backsliding.