How many soldiers saw action in World War 1?

Approximately 65 million soldiers served in various armies during World War I, with around 30 million seeing combat on the front lines. The war, which lasted from 1914 to 1918, involved many nations and resulted in significant casualties, with an estimated 9 million soldiers dying and millions more wounded. The scale of involvement varied widely among countries, with some nations mobilizing large portions of their populations for the conflict.