The author writes that by Poland not opposing Adolf Hitler in September 1939, the Second World War starts on April 9, 1940 by a German attack on Western Europe. After capturing Paris and defeating Belgium, the Netherlands, Norway, Denmark and France, on June 21, 1941, the Wehrmacht, together with the Polish Army, invades the Soviet Union. By the winter of 1941-1942, the Soviet Union ceases to exist. Poland and Germany divide its territory, but soon, mutual relationships deteriorate. Meanwhile, Germany keeps fighting the United Kingdom and the United States. The war is costly, and by 1944, all of the main units of the Wehrmacht are in Western Europe fighting the Allies, who land in France in summer 1944. In those circumstances, Warsaw begins secret negotiations with London and Washington and eventually switches sides and attacks the Third Reich in 194As Zychowicz writes, "At this point, Poland should have acted like Romania and Hungary in late stages of World War II. Noticing German problems in the West, both countries initiated secret negotiations with the Allies. The British and the Americans gladly accepted the offer, understanding that it would weaken the potential of the Axis powers".