While focusing on technological advances that can increase lethal capabilities of the Total Force, the U.S. Department of Defense has long recognized the critical importance of warfighters’ non-material lethality. Assuming that humans have a natural aversion to kill, most military training efforts to turn civilians into service members capable of using lethal force have focused on desensitization and compliance with military duties and ethics. However, empirical evidence has yet to be produced to support this assumption, and there is a need for a reexamination of how to psychologically prepare military troops to kill when it is ethical and not to kill when it is not ethical to do so. This paper offers suggestions for how DOD might advance the development of ethical lethality training.