Action packed photos show how as the 1940s opened the world sank into conflict. Adolf Hitler s troops marched through Europe. Japanese forces spread out across Asia and the Pacific Ocean. America hoped to avoid the war but could not. A surprise attack on Pearl Harbor, Hawaii, outraged the nation. World War II quickly engulfed the planet. Americans grimly accepted the challenge of war. Millions joined the armed services. Women worked long hours in factories and shipyards. Fierce battles raged overseas. Slowly, America and its allies scored key victories. The intense flash of an atomic bomb came in 1945. World War II ended and a new era began. Read how it all happened in the 1940s.