Tunisia, the birthplace of the 2011 Arab Spring, is now the largest source of foreigners fighting with the Islamic State. Prior to the Arab Spring, the Tunisian government maintained a half-century of aggressive secularism, banning the veil and most displays of piety, as well as jailing thousands of suspected Islamists. After the uprising, the moderate Islamist-led government introduced new religious freedoms, which were then exploited by Islamist radicals to incite violence. The government has responded by emphasizing public security, and this in turn appears to be generating repression and anger that further fuels the cause of the radicals. The lesson to be learned here is not that religious freedom is a cause of radicalization in Muslim-majority countries, but rather that when populations are denied religious freedom for extended periods of time, they become more susceptible to the destabilization of peaceful religious practice in favor of violent religious extremism.