It was history's greatest catastrophe. More than five decades after it ended­, years marked by constant conflict in at least some parts of the world and by enormous improvements in weaponry and fire-power, ­World War II remains by far the most costly war of all time. As many as 50 million people died, a majority of them in their teens and early twenties. The war had a cataclysmic effect on world politics, economics, and social life. Empires disappeared, others sprang up. Allies became enemies, enemies turned into allies. This book is by no means the whole story of the war. Its only aim is to cover the essential history of this greatest of human tragedies, and to recreate a feeling of what it meant in terms of the people who were swept up by it.