This chapter examines the ways in which so‐called ‘financial warfare’ positions banks and financial institutions on the frontline of security practice, amounting to what I call a finance–security assemblage. In the pursuit of terrorism financing, money comes to be considered as a ‘tool of combat’. This chapter examines the interconnections between finance and security in the post‐9/11 context, and analyses the novel spatial configurations that have accompanied the pursuit of terrorist monies. It focuses on the case of banking conglomerate HSBC, which incurred a record fine for circumventing US OFAC sanctions and prohibition. Unpacking this case shows how jurisdiction in this domain is articulated as transactional rather than territorial. It demonstrates how financial warfare profoundly impacts financial practices, shifting banks’ risk calculations and client profiling, and rerouting global financial flows.