The United States has engaged in several years of war in Iraq against the Islamic State (IS) since launching Combined Joint Task Force – Operation Inherent Resolve in October 2014. The United States estimates that they have killed more than 60,000 IS members, conducted more than 22,000 airstrikes and trained more than 100,000 security forces throughout Iraq. The successful U.S. campaign is in contrast to past operations in Iraq, Afghanistan, and elsewhere and is best encapsulated in the “by, with, and through” approach of letting Iraqis lead operations. This bottom-up approach is tactically successful but is short on strategy, opening the door for Iranian influence in Iraq. The United States is modeling other counterterror operations throughout the world on its Iraq success with other “build partner capacity” programs. Based on two years of fieldwork and interviews, this article examines both the tactical successes and policy implications of the U.S. successes against IS in Iraq.