Chapter 9 examines how nuclear strategy and covert action reshaped constitutional war powers during the mid–1950s and early–1960s – a period without large-scale wars but marked by major constitutional change. It argues that the most consequential adaptations arose from peacetime strategy rather than battlefield necessity. Nuclear weapons shifted constitutional attention from the authority to wage war to the authority to threaten it. Deterrence, built on speed, secrecy, and existential risk, favored rapid presidential decision-making, broad congressional delegations, and new assumptions about executive control of escalation. These developments were not technologically inevitable; they reflected strategic choices about how nuclear weapons would be used and restrained, with Congress enabling new arrangements through funding and advance authorizations. At the same time, the chapter traces a parallel constitutional track for covert warfare, as CIA paramilitary operations and proxy conflicts managed rivalry below open hostilities but with thinner legal foundations. Together, these developments reveal how war powers evolved through sustained congressional–presidential cooperation to manage escalation without major war.