In the post-Saddam era, differences among Iraqi ethnic and religious groups will either emerge as a barrier to political cooperation and national unity, or they will instead be mitigated as part of the struggle to define a new and more inclusive system of government. Should Iraqi ethnic and sectarian differences become unmanageable, a violent struggle for political power may ensue. This study does not predict an ethnic or sectarian civil war in Iraq except as a worst case, which must be analyzed and considered. If Iraqi violence erupts along religious/sectarian and ethnic lines, this conflict will have thunderous echoes throughout the area. Group identity, which is critical throughout much of the Middle East, will provide a compelling context for regional bystanders watching ethnic and sectarian bloodshed. Moreover, various nations would involve themselves in the fighting in ways up to and including the possibility of military intervention. Additionally, inter-communal harmony and tolerance in other regional states may suffer as the result of Iraqi fighting and the responses of neighboring governments to that fighting. The danger of an Iraqi civil war requires serious U.S. cooperation with those regional states that also have a stake in preventing this outcome.