In May 2017, Operation Temperer – the deployment of British military personnel in support of the police following a terrorist attack or the threat of such an attack – was activated for the first time. The deployment of uniformed armed personnel as a core element of the U.K.’s CT capability represents a significant and, in the authors view, welcome shift in how successive administrations have utilized aspects of state power in response to a terrorist threat or incident. Little academic work has been devoted to explaining how and why this change occurred, with the military moving from reluctant participants in domestic CT missions, to playing a central (and public) role in providing capacity for domestic security, as witnessed under Operation Temperer. This article charts the evolution of greater military involvement in domestic counter-terrorism missions after 9/11, revealing that a decade of policy paralysis was finally broken by the combination of terrorist events in Paris in January 2015, and the intervention of a forward leaning prime minister overcoming institutional reluctance on the part of the Ministry of Defence and other government departments to put British troops on British streets.