World war II was the deadliest military conflict in history in Absolute terms of total casualties. Over 60 million people were killed, which was about 3% of the 1940 world population (est. 2.3 billion).
European countries according to the number of deaths in World War 2
World countries according to the number of deaths in World War 2
Geographically it was the most widespread war, with major land combat on four continents.
WW2 Allied Bombings
Western Allies air missions through WW II