This thesis examines the U.S. government’s perceptions of its primary and peer-level nuclear competitor, Russia, in the post-cold war era. Drawing on prior research on Russian signaling, and on (nuclear) deterrence in action – the thesis employs deterrence theory and ontological security to examine how U.S. administrations’ views have evolved from Clinton to Biden. The thesis concludes that publicly communicated views on Russian nuclear capabilities change from initial optimism to, after Russia’s attack on Ukraine 2014, suspicion and even to some extent hostility. Ontological security, combined with deterrence theory, explains how complex narratives are found to be central to understanding how the U.S. government views Russian nuclear postures and capabilities – and while traditional deterrence theory provides a useful foundation for interpreting these evolving views – ontological security allows a more comprehensive understanding of underlying rationality and perceptions.