Of the total number of deaths in World War II , approximately 85 per cent — mostly Soviet and Chinese — were on the Allied side . Many of these deaths were caused by war crimes committed by German and Japanese forces in occupied territories . An estimated 11 to 17 million civilians died as a direct or as an indirect result of Nazi racist policies , including mass killing of around 6 million Jews , along with Roma , homosexuals , at least 1.9 million ethnic Poles and millions of other Slavs ( including Russians , Ukrainians and Belarusians ) , and other ethnic and minority groups . Between 1941 and 1945 , over 200,000 ethnic Serbs , along with gypsies and Jews , were persecuted and murdered by the Axis-aligned Croatian Ustaše in Yugoslavia . Also , over 100,000 Poles were massacred by the Ukrainian Insurgent Army in the Volhynia massacres , between 1943 and 1945 . At the same time about 10,000 – 15,000 Ukrainians were killed by the Polish Home Army and other Polish units , in reprisal attacks
Japanese forces
Japanese war crimes
World War II