Overview: Only a couple of decades after the end of the First World War--which was supposed to be the War that Ended All Wars--another, bigger, farther-flung, more destructive, and deadlier war began. Today, you'll learn about how the war in Europe progressed, from the Molotov-Ribbentrop pact and the invasion of Poland, to the Western and Eastern fronts, to VE Day and the atom bombs used in Japan.