World War I VS World War II

The First World War was fought from 1914 to 1918, while the Second World War was fought from 1939 to 1945. They were both the largest military conflicts in human history, but there were some differences between them.

Casualty

In total deaths, there were more than 60 million deaths in WWII, while 17 million were in WWI.

Time

Though WWII killed twice as much military as WWI, that war was twice as long and involved far more people. Thus, the density of military deaths in some pitched battles was a lot more in WWI.

Weapon

WWI pioneered using weapons of mass destruction, including chlorine gas, diphosphine gas, etc. However, due to the horrible experiences in WWI, no chemical weapons were used in Europe in WWII.