During World War II, the OSS liaison officer to Josip Broz Tito’s Communist Partisans was American agent Major Linn “Slim” Farish. Farish’s accounts helped decisively to switch Allied support away from Draza Mihailovich and to Tito. But who was Farish and how credible were his reports? New evidence from the Venona decrypts reveal that he may have been an agent allegedly working for Soviet intelligence. British Brigadier Fitzroy Maclean of the Special Air Services (SAS), a special forces unit of the British Army, referred to him in Eastern Approaches (1949) as “my American chief of staff”. Was Linn Farish, like...