Into the Shadows is a stark reminder of how radical elements from Iran’s Islamic Republic have helped foster the global network of militant Islam for over two decades. Despite efforts to liberalize, Iran cannot break with its past and remains a hub for Islamists worldwide. The blame, in Rubin’s view, falls squarely on Iran’s mullahs and their vigilante groups.

Rubin, who has spent time in Iran, finds that these vigilante groups are directly sponsored by Iran’s hardline clerics. Their activities ensure that Iran remains a breeding ground for militant Islam. His excellent study documents the activities of today’s vigilante groups (Ansar-i Hizbullah, the Sa‘id Imami Gang, and Fiday’iyan-i Islam) as well as those that enforced Islamic extremism in the days immediately following the Islamic revolution (Hujjatiyyah, Students Following the Line of the Imam, and the Mehdi Hashemi Gang). The members of these groups, interestingly, have a history of moving freely from one group to another within the radical Iranian network.

American policy toward Iran and these groups is on track, writes Rubin. Despite some warming in recent years, Iran remains a rogue regime in Washington’s eyes. So, although these radical groups represent only a small minority of the population, the U.S. government holds Iran accountable for the entirety of their actions. Rubin holds that America must stay the course of sanctions and cool relations. If Iran is to truly evolve, moderates must have an incentive to reverse the poisonous influence of radicals who continue to stymie Iran’s democratic development and support world terror.