This monograph considers the issues of Iranian influence in Iraq, and its impact on continuing sectarian violence there. It also questions the claims that a Shi'a crescent of power is solidifying by examining the distinct features of Iraqi versus Iranian Shi'ism and political Islam. Iran and Iraq have historically influenced and threatened each other. Today, the situation has been further complicated by the post-2003 change in the Iraqi Shi'a community's status, Iran's development of a nuclear program, and international efforts to contain that program. These issues are now influenced by a new pattern of Iraqi-Iranian, U.S.-Iraqi and Iranian-U.S. dynamics. This new triangle of state relations must also be considered in light of Iraq and Iran's neighbors.