The German invasion of the Soviet Union started on 22 June 1941 and led to a German military occupation of Byelorussia until it was fully liberated in August 1944 as a result of Operation Bagration. The western parts of Byelorussia became part of the Reichskommissariat Ostland in 1941, and in 1943, the German authorities allowed local collaborators to set up a regional government, the Belarusian Central Rada, that lasted until the Soviets reestablished control over the region. Altogether, more than 2 million people were killed in Belarus during the three years of Nazi occupation, almost a quarter of the region's population, including 500,000 to 550,000 Jews in the Holocaust in Belarus. Background The Soviet and Belarusian historiographies study the subject of German occupation in the context of contemporary Belarus, regarded as the Byelorussian Soviet Socialist Republic (BSSR), a constituent republic of the Soviet Union in the 1941 borders as a whole. Polish historiography insists on special, even separate treatment for the East Lands of the Poland in the 1921 borders (alias "Kresy Wschodnie" alias West Belarus), which were incorporated into the BSSR after the Soviet invaded Poland on 17 September 1939. More than 100,000 people of different ethnic backgrounds, mostly Poles and Jews in West Belarus, were imprisoned, executed or transported to the eastern USSR by Soviet authorities before the German invasion. The NKVD (Soviet secret police) killed more than 1,000 prisoners in June and July 1941, for example, in Chervyen. Invasion After twenty months of Soviet rule in Western Belarus and Western Ukraine, Nazi Germany and its Axis allies invaded the Soviet Union on 22 June 1941. Eastern Belarus suffered particularly heavily during the fighting and German occupation. Following bloody encirclement battles, all of the present-day Belarus territory was occupied by the Germans by the end of August 1941. With Poland regarding the Soviet annexation as illegal, the majority of Polish citizens did not ask for Soviet citizenship from 1939 to 1941, and as a result were Polish citizens under Soviet and later German occupation. Occupation In the early days of the occupation, a powerful and increasingly well-coordinated Soviet partisan movement emerged. Hiding in the woods and swamps, the partisans inflicted heavy damage to German supply lines and communications, disrupting railway tracks, bridges, telegraph wires, attacking supply depots, fuel dumps and transports, and ambushing Axis soldiers. In one of the most successful partisan sabotage actions of the entire Second