Today zombies are all the craze, but the first depiction of the "undead" was in a World War I film, "J'Accuse." What makes it almost tragic is that the extras who played the dead returned were actual French soldiers who filmed the scenes before returning to the front. By the time the film was released in 1919, many of those men were dead.

The Living Dead in War Films: It Began With J’Accuse
The Living Dead in War Films: It Began With J'Accuse - The Mag Life