This article assesses Iran's strategy in dealing with the threat of the Islamic State in Iraq and Syria (ISIS). It examines the implications of the rise of ISIS in Iran's immediate neighbourhood for Tehran's policies in Syria and Iraq and investigates how each of these countries affects Iranian national interests. It provides an overview of the major events marking Iran and Iraq's relations in the past few decades and discusses the strategic importance of Iraq for Iran, by looking at the two countries' energy, economic and religious ties. It also considers Iran's involvement in Syria since the beginning of the Syrian conflict.

Existing scholarship assumes that transnational insurgents strengthen domestic rebels. Analysis of transnational insurgents’ participation in the Chechen wars, however, reveals that foreign fighters can weaken a domestic opposition movement by introducing goals and tactics that divide the movement and alienate the local community. To avoid this outcome, domestic resistance leaders must adapt the foreigners’ ideas to the local context.

April marks the tenth anniversary of the overthrow of Saddam Hussein by the United States and its partners. At this juncture, it is reasonable for Americans—and Iraqis and others—to ask whether the past decade of U.S. involvement in Iraq was worth it. Did the large human and financial costs produce an outcome that justifies the sacrifice?