This article examines patterns of collective violence in Iraq since the 2003 invasion, focusing particularly on gender-based violence and militia activities. Drawing on the work of Charles Tilly and others, it explores the idea that collective violence follows a 'logic' that can be observed in a wide variety of historical and cultural contexts. An aspect of the 'logic of violence' that emerges as particularly important is that of 'dual purpose violence', which simultaneously serves two or more goals of individuals, groups and political organizations. Activities which in some respects serve relatively conventional criminal processes can simultaneously be part of processes of state-building, which in the context of Iraq means not only the consolidation of central government power but the building of numerous state-like power structures at local and regional level. Table and references (Published Abstract)