How do you credibly communicate a threat that you cannot reveal? This problem is endemic for modern space and cyberspace capabilities, but the challenge of secrecy constraints in cross-domain deterrence is not a new phenomenon. During the late Cold War, nuclear forces deterred conventional attack, theater nuclear forces deterred strategic nuclear escalation, and conventional threats to nuclear capabilities deterred conventional attack. Some of these capabilities, particularly intelligence collection and electronic datalinks, depended on sensitive tactics and technologies that could not be revealed lest the enemy develop effective countermeasures. Secrecy created uncertainty about the true balance of power, which should have made conflict more likely, according to rationalist theory. This chapter shows, however, that the United States was able to use several mechanisms to communicate its capabilities to the Soviet Union without thoroughly compromising the ability to use them. Leveraging historical evidence from senior Soviet leadership, the chapter argues that U.S. nuclear counterforce strategy, which leveraged clandestine capabilities in many domains, nevertheless was effective in shaping Soviet perceptions and influencing Soviet policy.
