During the 18th century, a worldwide trend emerged in which civilians commanded the military. World War I reversed this trend in the early 20th century. Mills writes that "the Constitution was founded in fear of a powerful military establishment" (176), noting that it designates the President "a civilian commander in chief" (176) and that only Congress may declare war. After the Revolutionary generation, the American elite did not include military men, yet about one half of the 33 US Presidents (at the time of Mills’s writing) had military experience, including nine generals and six career officers. From Shays’ Rebellion in the 1780s to the Korean War in the 1950s, the US has never been long at peace. Historically, a decentralized militia system of armed citizens bolstered American democracy. Until World War I, the federal government did not have a monopoly on the tools of violence, and military action did not require the discipline of permanent training. Civilians ruled over the military. In the late 19th century, the military had a "half-professionalized high officer corps" (183) who did not belong to the American elite, which consisted of men in business and politics.

By the mid-20th century, conditions are different.