Following the German invasion of Yugoslavia in April 1941, Mihajlović became head of the Četnik guerrilla movement, which was loyal to the Yugoslav government-in-exile in London. The Četniks, along with the communist partisans led by Josip Broz Tito, resisted the occupying German forces. Although the two groups initially rallied around a common cause, political differences eventually led to mutual distrust that erupted into open armed conflict between them.
Mihajlović, promoted to the rank of general in January 1942, followed the policy of the exiled royal government, which called for restrained resistance until Allied forces could provide more assistance. The communists conducted an aggressive resistance campaign that resulted in German reprisals against the civilian population, but beginning in 1943 the British government, which had charge of support for the Yugoslav resistance, channeled its aid entirely to Tito and the communists.
Tito's partisans largely liberated Yugoslavia, and his provisional government dissolved the Četniks. Mihajlović went into hiding but was eventually captured on 13 March 1946. Despite Western protests, Tito's government put Mihajlović on trial. The trial of Mihajlović and twenty-three other former royalists began in Belgrade on 10 June 1946. The court almost immediately concluded that Mihajlović had considered communism a greater threat than the Axis powers. Although he denied being a German collaborator and having incited civilian massacres, he was convicted and sentenced to death along with ten others. Mihajlović was executed by a firing squad in Belgrade on 17 July 1946. The execution created the myth of Mihajlović as a protector of Serbian interests, which resurfaced during the 1990s and was exploited by Serb nationalists.
Tomasevich, Jozo. The Chetniks: War and Revolution in Yugoslavia, 1941–1945. Stanford, CA: Stanford University Press, 1975.; Trew, Simon. Britain, Mihailović and the Chetniks, 1941–42. New York: St. Martin's, 1998.