The model for mass-murder—the genocide of the Jews—evolved out of the First World War. Many nations of the world systematically slaughtered their own people. Building upon this template, Hitler adopted one of its killing methods: poison gas.

"All the capacity of industrial society—straining at the bit for destruction. One of the French soldiers called it extermination. I call it routinized, mechanized genocide: The genocide of people on their own citizens." Professor Weiner at 22:05 of the video.

First World War Casualties