Third Anti-partisan Offensive - Aftermath

Aftermath

After clearing the larger towns of the Birač region of Partisans and Chetniks, the Black Legion committed large-scale atrocities against Serbs and Jews in the region, including massacring about 890 people from Vlasenica after raping the women and girls.

Along with the three East Bosnian Shock Battalions, the Partisan General Staff of Bosnia-Herzegovina first attempted to cross the Bosna to follow the Partisan Supreme Staff and main force to western Bosnia, but instead retreated to Birač, where they joined forces with the Birač Detachment at the end of May. The Birač Partisan Detachment was the only Partisan or volunteer detachment in East Bosnia not to suffer a pro-Chetnik coup in March–May 1942. By June–July 1942, the Partisans in eastern Bosnia had been reduced to a strength of around 600 fighters.

Operation Trio was followed up by the joint Italian-Chetnik Herzegovina Offensive against Partisan detachments within the Italian zone of occupation in eastern Herzegovina and Montenegro, with similar effects: the Partisans lost almost all of the liberated territory in these areas. This follow-up offensive is also considered part of the Third Enemy Offensive in Yugoslav historiography. After Operation Trio, NDH forces remained south of the demarcation line between the German and Italian zones of occupation, in spite of protests from the Italians.

After Operation Trio and the follow-up offensive, the Partisans formed three more Proletarian Brigades, consisting mainly of Montenegrins. Operation Trio contributed to the decision of the Partisan Supreme Staff to withdraw to western Bosnia in the Partisan Long March, which commenced in late June 1942.

While incurring significant casualties fighting the Black Legion, the Chetnik movement in eastern Bosnia benefited from the mass desertion of Partisans and the many pro-Chetnik coups in Partisan and volunteer detachments. Despite their lack of unity, the Chetnik movement thrived in eastern Bosnia for the reminder of 1942 because some Chetnik leaders made accommodations with the Ustaše regime and as many Chetniks and Partisans were unwilling to kill fellow Bosnian Serbs of the opposing faction.