Though the Islamic State's core territory is now shrinking, its rapid rise as a global enemy and its quick territorial expansion in 2013 and 2014 shook the Middle East, instigating a series of realignments of military power. As the militant group claimed Mosul, Tikrit, Sinjar, Zumar and Kobani, Kurdish peshmerga units of Iraqi, Iranian, Turkish and Syrian nationality deployed to try to stop it. Today, the multi-country front against the Islamic State is more secure and stable in those areas where territory held by the group abuts traditionally Kurdish territory. At the same time, however, the Kurdish groups' involvement in the fight against the Islamic State has once again empowered them militarily. In Iran, home to a substantial Kurdish minority population, the side effects of this newfound might are visible....