Nuclear weapons altered the relationship between the American state and its citizens in the early years of the Cold War. From the 1945 Trinity Test forward, Americans grappled with the consequences of the nuclear weapons revolution. Among other challenges facing the nation, it was clear that military defense against a nuclear strike was nearly impossible and civilian preparation programs could cost billions of dollars. Should deterrence peacekeeping fail, Americans would face an attack without military protection, making large-scale civilian casualties unavoidable. "And yet," Senator Brien McMahon puzzled in 1950, "the first duty of a sovereignty is to protect its people." Nuclear weapons unsettled Americans' ideas about federal protection, individual responsibility, and public safety. Under the threat posed by nuclear technology, these conflicting concerns shaped domestic and international policy and framed national community in the Atomic Age.