This occasional paper examines the link between political finance and corruption in the arms trade. It draws on the World Peace Foundation’s Compendium of Arms Trade Corruption, a collection of 29 cases of corruption in the arms trade and the broader military sector from around the world, each containing a standard set of summary information along with a narrative description. The arms trade has many features that make it highly susceptible to corruption. This paper makes the case that it also has four key features that tie it particularly closely to political competition and political finance.