The 1925 Geneva Convention banned the use of chemical weapons. This was an agreement that even Hitler was willing to keep. However, Hitler's concerns with chemical weapons arose out of a personal hatred. He had been subjected to chemical attacks during the First World War, and thus could not countenance the idea of unleashing them in war again. This "mercy" did not extend to weapons of a biological nature.
The Germans largely ignored biological warfare development during the days of the Weimar Republic, but this changed with the rise of the Nazi Party. The Nazis' obsession with race led to an obsession with the human anatomy, and the concentration camps that were springing up around the Third Reich gave the Nazis' brightest and most morally challenged biological scientists plenty of test subjects. Chief among these was Josef Mengele, an anthropologist and medical officer in the SS. Mengele's research, which began with surgical modifications on political prisoners, interested the SS lea