 In April 1942 the Communists in Bosnia established two Shock Anti-Chetnik Battalions (Grmeč and Kozara) composed of 1,200 best soldiers of Serb ethnicity to struggle against Chetniks.Later during the war, the Allies were seriously considering an invasion of the Balkans, so the Yugoslav resistance movements increased in strategic importance, and there was a need to determine which of the two factions was fighting the Germans.A number of Special Operations Executive (SOE) agents were sent to Yugoslavia to determine the facts on the ground.