On September 1, 1939, German forces stormed into Poland, precipitating nearly six years of savage, unrelenting warfare that would leave large areas of Europe in ruins. For the first three years, the Wehrmacht seemed invincible. The swift victory in Poland was followed by the rapid conquest of Denmark and Norway. In May 1940, the Wehrmacht launched the Blitzkrieg ("lighting war") in the west, overwhelming Holland and Belgium in a matter of days, driving the British Expeditionary Force back across the English Channel, and completing the defeat of France within a month. Further victories followed in the Balkans, Greece, and North Africa. The opening months of the invasion of Soviet Russia, Operation Barbarossa, proved equally successful, with the German panzers being halted just short of Moscow amidst the harsh conditions of the Russian winter. - Jacket flap.