World War II, the most massive and appalling military conflagration in history began on September 1, 1939 when Hitler's troops invaded Poland and from there, it spread inexorably in all directions. On December 7 1941, the Japanese bombed Pearl Harbour, thus bringing the huge American armies into the picture and the Pacific was ablaze as Japan and America fought a devastating island-hopping war across the ocean. As well as swallowing millions of lives, the demands of the military machine gave rise to the atom bomb and the computer; the British Empire was dying but the Commonwealth was heralded; the war made Churchill and  the 'spiv'; it created rationing and the Welfare State; it slaughtered 6,000,000 Jews, broke marriages and laid waste to the European economy.  This is a graphic account of the fateful years that changed the world forever. Illustrated with black and white photos.