This article seeks to explain the historically poor performance of the US Department of Defence’s security force assistance (SFA) to state and non-state armed forces to counter terrorism. The... Show moreThis article seeks to explain the historically poor performance of the US Department of Defence’s security force assistance (SFA) to state and non-state armed forces to counter terrorism. The article argues that the dominant understanding of SFA as a one-way, top-down relation between a principal (sponsor) and an agent (recipient) has neglected the socio-political dynamics and effects of the intervention. Studying the socio-political processes reveals the messy reality on the ground and how difficult, if not impossible, it is to fully control the operation and the participating recipients. Rather than controlling recipients, this article argues that SFA should be concerned with negotiating the multiple and diverse interests, needs, and priorities. This claim will be substantiated with an in-depth, qualitative case study of Operation Inherent Resolve in Iraq between 2014 and 2018. Show less