section_path: History/World War II
section_name: World War II
paragraph_text: World War II
  
  Following the Invasion of Poland in September 1939, German and Soviet troops divided the territory of Poland. Thus, Eastern Galicia and Volhynia with their Ukrainian population became part of Ukraine. For the first time in history, the nation was united. Further territorial gains were secured in 1940, when the Ukrainian SSR incorporated the northern and southern districts of Bessarabia, Northern Bukovina, and the Hertsa region from the territories the USSR forced Romania to cede, though it handed over the western part of the Moldavian Autonomous Soviet Socialist Republic to the newly created Moldavian SSR. These territorial gains of the USSR were internationally recognized by the Paris peace treaties of 1947.
  
  German armies invaded the Soviet Union on 22 June 1941, initiating nearly four years of total war. The Axis initially advanced against desperate but unsuccessful efforts of the Red Army. In the battle of Kyiv, the city was acclaimed as a " Hero City ", because of its fierce resistance. More than 600,000 Soviet soldiers (or one-quarter of the Soviet Western Front) were killed or taken captive there, with many suffering severe mistreatment. After its conquest, most of the Ukrainian SSR was organised within the Reichskommissariat Ukraine, with the intention of exploiting its resources and eventual German settlement. Some western Ukrainians, who had only joined the Soviet Union in 1939, hailed the Germans as liberators, but that did not last long as the Nazis made little attempt to exploit dissatisfaction with Stalinist policies. Instead, the Nazis preserved the collective-farm system, carried out genocidal policies against Jews, deported millions of people to work in Germany, and began a depopulation program to prepare for German colonisation. They blockaded the transport of food on the Dnieper River.
  
  Although the majority of Ukrainians fought in or alongside the Red Army and Soviet resistance, in Western Ukraine an independent Ukrainian Insurgent Army movement arose (UPA, 1942). It was created as the armed forces of the underground Organization of Ukrainian Nationalists (OUN). Both organizations, the OUN and the UPA, supported the goal of an independent Ukrainian state on the territory with a Ukrainian ethnic majority. Although this brought conflict with Nazi Germany, at times the Melnyk wing of the OUN allied with the Nazi forces. From mid-1943 until the end of the war, the UPA carried out massacres of ethnic Poles in the Volhynia and Eastern Galicia regions, killing around 100,000 Polish civilians, which brought reprisals. These organized massacres were an attempt by the OUN to create a homogeneous Ukrainian state without a Polish minority living within its borders, and to prevent the post-war Polish state from asserting its sovereignty over areas that had been part of pre-war Poland. After the war, the UPA continued to fight the USSR until the 1950s. At the same time, the Ukrainian Liberation Army, another nationalist movement, fought alongside the Nazis.
  
  In total, the number of ethnic Ukrainians who fought in the ranks of the Soviet Army is estimated from 4.5 million to 7 million; half of the Pro-Soviet partisan guerrilla resistance units, which counted up to 500,000 troops in 1944, were also Ukrainian. Generally, the Ukrainian Insurgent Army's figures are unreliable, with figures ranging anywhere from 15,000 to as many as 100,000 fighters.
  
  The vast majority of the fighting in World War II took place on the Eastern Front. The total losses inflicted upon the Ukrainian population during the war are estimated at 6 million, including an estimated one and a half million Jews killed by the Einsatzgruppen, sometimes with the help of local collaborators. Of the estimated 8.6 million Soviet troop losses, 1.4 million were ethnic Ukrainians. The Victory Day is celebrated as one of eleven Ukrainian national holidays.