The United States military has long led the world in the development and employment of positioning, navigation, and timing (PNT) in its operations. Military PNT capabilities have become vital to the military’s ability to shape the global environment, deter aggression, and fight and win wars, now and in the future. This reliance on PNT, and particularly the U.S. Global Positioning System (GPS), has created an attractive point of attack which adversaries will increasingly target. U.S. and allied forces will be challenged to maintain mission effectiveness in environments in which PNT information is denied, degraded, or spoofed across nearly every phase of military operations. To strengthen national defense, the Department of Defense and the private sector must work together to create resiliency within the military’s existing GPS enterprise, create sources of PNT that enable robustness and resilience, and find ways to disrupt adversaries’ use of PNT information.