Country Lead: Jacob N. Shapiro Following the U.S. invasion in March 2003 Iraq suffered a lengthy civil war in which over 100,000 civilians were killed, tens of thousands of combatants died, and millions were temporarily—and sometimes permanently—displaced. The war featured at least three distinct conflicts: a sectarian civil war between Sunni and Shi’ite militias; an insurgency by mostly Sunni militias, some Iraqi and some international, against the government of Iraq and the Coalition forces supporting it; and a communal conflict pitting Kurds against Arabs in Kurdistan. During the period of peak violence in 2006 and 2007, there were over a thousand insurgent attacks per week in Iraq and hundreds of sectarian killings. The country regained a large measure of stability from 2008 through 2010 though political violence in Iraq continues at a substantial pace; 1,547 people were killed or injured in the 1,197 terrorist attacks in 2010. Studying the war in Iraq provides an opportunity to learn more about a range of conflict processes because precise geo-located data on violence are available for most of the war and because there is a rich set of secondary data sources available, from excellent historical work to the high-quality household surveys conducted by the Iraqi statistical agency and its international partners. ESOC research on Iraq has examined how labor market conditions affect insurgent violence, how people respond to civilian casualties perpetrated by different sides, how changes in communications technologies influence civil conflict, and which (if any) kinds of aid spending serve to enhance stability. ESOC data on Iraq span almost the entire war and include information on different kinds of violence, aid projects, population demographics, public opinion, cellular communications networks, basic infrastructure, hydrocarbon resources, and more.