On 1 Sept. 1939 German Nazi forces invaded Polish territory in Wieluń and Westerplatte. Following the secret Ribbentropp-Molotov pact, Soviet army attacked Eastern territory of Poland on 17 Sept. 1939. For five years Poland endured the most severe wartime occupation conditions in modern European history. Until May 1945 more than 5,5 mln citizens were killed, in battle-fields all over the Europe, in German and Soviet concentration camps, in street executions. Polish industry and economy was devastated, the capital - Warsaw - totally burned by Nazis after the Warsaw Uprising (1944).