The authors examined potential effects that emerging technologies could have on U.S. national security policy and identified long-term effects that these technologies might have on effectiveness and stability-two major aspects of deterrent relationships. They did this by pursuing several phases of analysis. First, they selected a specific set of eight technology areas from the numerous technologies that could play a role in shaping the practice of deterrence. The researchers then took several complementary steps to assess the problem of deterrence, competitors' views of it, and possible criteria for evaluating the effects of technologies. In parallel with these research efforts, they conducted in-depth assessments of each of the eight technology areas. Finally, they employed four discrete lines of analysis-four "lenses"-to generate possible causal relationships between the eight technology areas and deterrence outcomes. This report highlights two overarching findings of this analysis. First, collections of emerging technologies-especially in the realms of information aggression and manipulation, automation (including automated decision support systems), hypersonic systems, and unmanned systems-hold dramatic implications for both the effectiveness and stability of deterrence. Second, an emerging transition to new ways of warfare, empowered by these same emerging technologies, poses more general risks to U.S. deterrent policies than does any single technology or set of technologies. This research was completed in September 2020, before the February 2022 Russian invasion of Ukraine. It has not been subsequently revised.