Space stability, fundamental to U.S. national security interests, may be eroding. Potential enemies understand the high degree to which space systems enhance U.S. conventional warfighting capabilities, and a growing number of them are acquiring the ability to degrade or destroy those systems. The United States needs a coordinated national space deterrence strategy, one that begins with a policy that declares that the United States will punish space aggressors in ways, times, and places of its choosing. The United States should also take steps to reduce the benefits an enemy might expect to gain in attacking U.S. space systems.