CNAS: This report begins with a discussion of how the United States lost sight of great-power deterrence and why its legacy presence-reliant approach to deterrence is unsuited to the current challenge. Instead, the department should embrace deterrence by denial to improve simultaneous deterrence of China and Russia in the near term without consuming resources earmarked for modernization. The report redefines campaigning to demonstrate how it could support a denial strategy through the rigorous linkage of campaigning to warfighting. It develops a framework for how the U.S. Department of Defense could implement this revised approach to campaigning. The framework is applied to the Indo-Pacific and Europe to demonstrate how the United States can reimagine its forces and capabilities, posture, and activities to simultaneously deter China from aggressing against Taiwan and Russia from aggressing against the Baltics. These plans are analyzed to determine the implications of two-theater deterrence for U.S. defense strategy, peacetime activities, and resource management. Finally, the report concludes with recommendations for the DoD and Congress on how to manage the simultaneous threat of two major adversaries in the near term.