This compares to 15% of Poland's post war borders and 19% of Ukrainian population in post war border and comparing to 2% of Czechoslovakian population that perished in post war borders. Estimates on population losses in Ukraine range from 7 to 11 million. More than 700 cities and towns and 28,000 villages were destroyed. It is estimated that 1,700,000 people were killed during World War II in Yugoslavia from 1941 to 1945. Very high losses were among Serbs who lived in Bosnia and Croatia, as well as Jewish and Romani minorities, with losses also high among all other non-collaborating populations. In the summer of 1941, the Serbian uprising came at the time of the German invasion of the USSR. The Nazi response was the execution of 100 Serbian civilians for every killed soldier and 50 Serbian civilians for every wounded soldier. The Yugoslav Partisans fought both a guerrilla campaign against the Axis occupiers and a civil war against the Chetniks. The Independent State of Croatia was established as a Nazi puppet-state, ruled by the fascist militia known as the Ustaše. During this time the Independent State of Croatia created extermination camps for anti-fascists, communists, Serbs, Muslims, Gypsies and Jews, one of the most infamous being the Jasenovac concentration camp. A large number of men, women and children, mostly Serbs, were murdered in these camps. Britain and France, two of the victors, were exhausted and bankrupted by the war, and Britain lost its superpower status. With Germany and Japan in ruins as well, the world was left with two dominant powers, the United States and the Soviet Union. Economic and political reality in Western Europe would soon force the dismantling of the European colonial empires, especially in Africa and Asia. One of the most important political consequences of the Nazi experience in Western Europe was the establishment of new political alliances which eventually became the European Union and an international military alliance of European countries known as NATO to counterbalance the Soviets' Warsaw Pact and until communist rule in Eastern Europe ended in the late 1980s. The Communists emerged from the war sharing the vast prestige of the victorious Soviet armed forces, and for a while it looked as though they might take power in France, Italy and Greece. The West quickly acted to prevent this from happening, hence the Cold War. In Greece the German occupation (April 1941 – October 1944) destroyed the economy through war reparations, plundering of the country's resources and hyper-inflation. In addition, the Germans left most of the country's infrastructure in ruins as they withdrew in 1944.