World War II began in 1939 and ended in 1945. This defining period of history changed the identity of the United States—and its future. The country not only emerged as the leader of the free world, it also prospered from wartime advancements in the fields of technology, medicine, and science that were applied in new ways during the era of peace that followed the fighting. For anyone seeking evidence of what WWII contributed to modern life, look no further than computers. The war also gave us such everyday luxuries as the flu vaccine, penicillin, and microwave ovens. Harder to define, yet no less relevant, are the lessons of the conflict. WWII revealed deadly truths about unchecked power and the slippery slope of hatred. These are issues worth revisiting, even as the war that began 85 years ago moves further and further into the past. Here is the definitive story of WWII, told through stunning photography and vivid summaries of the most important turning points. Never Forget.