This article analyses the shifts in security and defence policies across the six states of the Gulf Cooperation Council (GCC) and disentangles political and geopolitical strains in the U.S.-Gulf relationship from practical measures to boost cooperation and deepen interoperability. In examining the trajectory of security and defence relationships, the article assesses the stability and durability of the underlying components of U.S.-Gulf partnerships in a time of rapid change. The article begins a section that details how and why the perception of U.S. disengagement has evolved, despite ongoing reliance on facilities such as Al-Udeid in Qatar for forward basing arrangements, before a second section examines regional responses to the withdrawal from Afghanistan in 2021, the Russia-Ukraine war in 2022, and the Israeli war in Gaza that erupted in 2023. A third section explores the ‘nuts and bolts’ of security and defence relationships and considers issues such as U.S. arms sales and Department of Defense programs, such as Red Sands in Saudi Arabia and the Comprehensive Security Integration and Prosperity Agreement with Bahrain, as ways to boost cooperation in the face of political tension and stiff competition. As U.S. troop levels have ebbed and flowed, a final section considers whether a more flexible approach to security relationships is sustainable in a far more transactional era of international power and politics.