Looking back, World War I is largely overshadowed by its not-so-innovatively named counterpart some two and a half decades later. But at the time, the conflict was called the “War to End All Wars” and the “Great War” because it was impossible for many, especially in Europe, to envision anything more horrific. At its height, it involved most countries in Europe, Asia, and Africa, several from the Americas, Australia, and numerous other scattered island nations. Lives were lost on an unprecedented scale, and the era witnessed the brutality of trench warfare and the advent of sinister new weapons. Although the United States made a fashionably late appearance and suffered only a fraction of the casualties (and none of the domestic destruction) endured by European states, the conflict was nonetheless grueling. For the first time, hundreds of thousands of Americans went abroad to fight, and many failed to return. This mobilization caused equally disruptive changes in and to the federal government's coffers, the American workplace, the neighborhood bar, and the ballot booth.

Like other chapters, this is not an attempt to document every domestic political effect wrought by war. Rather, this chapter identifies key themes that run consistently across major American wars. With regard to the American state, World War I's influence on the institutionalization of the income tax is highlighted. Tax policies, directly initiated by this war, created new and enduring layers of federal bureaucracy and have continued, to this day, to provide the government with most of its resources.