Soviet partisans were members of resistance movements that fought a guerrilla war against Axis forces during World War II in the Soviet Union, the previously Soviet-occupied territories of interwar Poland in 1941–45 and eastern Finland. The activity emerged after Nazi Germany's Operation Barbarossa was launched from mid-1941 on. It was coordinated and controlled by the Soviet government and modeled on that of the Red Army. The partisans made a significant contribution to the war by countering German plans to exploit occupied Soviet territories economically, gave considerable help to the Red Army by conducting systematic attacks against Germany's rear communication network, disseminated political rhetoric among the local population by publishing newspapers and leaflets, and succeeded in creating and maintaining feelings of insecurity among Axis forces. Soviet partisans also operated on interwar Polish and Baltic territories occupied by the Soviet Union in 1939–1940, but they had significantly less support there and often clashed with local national partisan groups, as well as German-controlled auxiliary police. After the German invasion of Poland in 1939, which marked the beginning of World War II, the Soviet Union invaded the eastern regions of the Second Polish Republic (referred to as the Kresy) and annexed the lands totalling with a population of 13,299,000 inhabitants including ethnic Belarusians, Ukrainians, Poles, Jews, Czechs and others. Soviet era sources state that in 1939, Soviet forces took control of regions of the Polish Republic that had "a population of more than 12 million, including more than 6 million Ukrainians and about 3 million Belarusians." The program of the partisan war was outlined in Moscow after the German attack in 1941 against the USSR. Directives issued on July 29, 1941 and in further documents by the Soviet People's Commissaries Council and Communist Party called for the formation of partisan detachments and 'diversionist' groups in the German-occupied territories.