The concept of national security originates in the 1930s, as part of a White House campaign in response to the rise of fascism. Before then, national self-defense was defined in terms of protecting sovereign territory from invasion. But President Franklin D. Roosevelt and his circle worried that the US public, comforted by two vast oceans, did not take seriously the long-term risks posed by hypermilitarization abroad. New Dealers developed the doctrine of national security, Andrew Preston argues, to supplant the old idea of self-defense: now even geographically and temporally remote threats were to be understood as harms to be combated, while ideological competitors were perilous to the "American way of life."

Total Defense shows it was no coincidence that a liberal like Roosevelt promoted this vision. National security, no less than social security, was a New Deal promise: the state was obliged to safeguard Americans as much from the guns and warships of Nazi Germany and imperial Japan as from unemployment and pov-erty in old age. The resulting shift in threat percep-tion among policymakers and ordinary citizens alike-transformed the United States, spearheading massive government expansion and placing the coun-try on a permanent war footing.