Lt. Col. Dave Grossman has spent his career researching, writing, and speaking about an unpleasant topic: killing. Specifically, what happens to a person physically and psychologically whenever they have to take the life another human to protect themselves or someone else. Grossman's work has provided invaluable insights on how to better train and prepare our warriors for the stress that comes with life and death situations. I talk to Lt. Col. Grossman about the often unspoken act of killing, the mind and body in combat, and what people can do to prepare themselves mentally and physically for violent situations.