The author describes the impact of stress and fatigue factors on the functioning of a battalion sized unit engaged in continuous combat operations during REFORGER 82. As fatigue and stress increased there was a corresponding decline in combat efficiency as reflected in errors of tacticle judgment, decreased map reading ability and impaired communication abilities on the part of unit leaders. Opportunities for effective preventive interventions by mental health personnel in a combat environment are described as are some considerations for handling stress casualties in a field environment.