This paper examines cross domain deterrence strategies involving cyber incidents. By focusing on efforts to halt Russian and Chinese cyber operations against the United States this paper examines the importance of developing, maintaining and implementing (when necessary) cross domain deterrence strategies. This paper departs from more theoretic debates on the value and potential success, or lack thereof relating to cyber deterrence strategies and focuses on two cases in which cross domain retaliations were utilized to halt adversary behavior. From these two cases this paper posits a preliminary theory of cross domain deterrence applicable to cyber interactions between states and advances the debates in the field by shifting the center of gravity away from within domain responses to other mechanisms to deter adversary behavior.Brantly 2 Deterrence in cyberspace is a vexing problem plagued a range of challenges including attribution, proportionality and capability. 1 For the better part of the last two decades scholars and practitioners have sought out solutions to the cyber deterrence conundrum by leaning heavily on nuclear analogies or conventional International Relations or criminological paradigms. 2 Parallels to more conventional kinetic attacks are hampered for a variety of reasons, largest of which appears to be a lack of cognitive equivalence between kinetic and cyber means to achieve the same effect. 3 This lack of equivalence often constrains decision-making to within domain response options often predicated on deterrence strategies by denial or punishment within cyberspace. Rarely do cyber activities at the nation state level result cross-domain responses. Tim Maurer lists the two cyber actors most threatening based on capabilities as Russia and China. 4 Both China and Russia have, over the last 20 years, engaged in substantial cyber operations against the United States in the form of attacks against critical infrastructure or sustained economic espionage. The United States has engaged in moderate efforts at deterring both actors external to cyberspace. These efforts have had markedly different effects on the types and continuance of cyber-attacks against the United States.The data pool of cross-domain deterrence in response to cyber-attacks is limited within the public domain. The two most prominent cases to date are U.S. efforts to deter for-profit economic espionage by Chinese actors and efforts to deter Russian information operations and cyber intrusions into U.S. election processes and infrastructures. This chapter focuses on these two instances of cross-domain responses and assesses the strategic impact of these actions on the status quo of state to state interactions. This chapter argues that by signaling to an attacking nation a clear and credible cross-domain response the United States is able to alter the framing and lack of 1 Brantly, Aaron F.Brantly 3 cognitive equivalence of between kinetic and cyber-attacks while simultaneously managing potential escalatory concern. Cross-domain responses b...