The Age of Youth tackles the complicated relationship between youth, national security, and education from World War I to World War II. It reveals how the United States created a time-specific political and social category of youth that relied on the expectation that military-age men should devote themselves to the future of their country. Analyzing policies from the Reserve Officers' Training Corps, the New Deal, wartime military training programs, and those governing the post-World War II occupation of Japan, Masako Hattori demonstrates that the priorities of national security conditioned young people's access to education in the US in the first half of the twentieth century, in both wartime and peacetime, and explores how the evolving link between youth, education, and national security shaped and reshaped the cultural concept of “youth” in American society.