Increased reliance on intelligence processing, exploitation, and dissemination; networked real-time communications for command and control; and a proliferation of electronic controls and sensors in military vehicles (such as remotely piloted aircraft), equipment, and facilities have greatly increased the U.S. Department of Defense (DoD)'s dependence on energy, particularly electric power, at installations. Thus, ensuring that forces and facilities have access to a reliable supply of electricity is critical for mission assurance. However, most of the electricity consumed by military installations in the continental United States comes from the commercial grid-a system that is largely outside of DoD control and increasingly vulnerable to both natural hazards and deliberate attacks, including cyberattacks. In this report, researchers explore two approaches that DoD might consider as options for deterring attacks against the power grid: enhancing resilience and reliability to deter by denial and using the threat of retaliation to deter by cost imposition. The report represents a first step in developing frameworks and context to support DoD decisionmaking in this area.