Lifesavers turned into butchers. Enlighteners became torturers. What twisted and corrupted humanity? And how did they escape any trial after WWII, living free and in peace? CGTN presents the documentary "Behind Unit 731 - The Butchery of Humanity by War and Militarism," a chilling exploration of one of the darkest chapters in human history. It takes you deep into how Japan's militarism transformed men into monsters – and why, even 80 years later, there remains fertile soil for the seeds of evil to grow again.