Americans had traditionally prided themselves on being able to maintain a small army. Protected by two oceans and following George Washington’s plea to avoid entangling alliances with the Europeans, they had fought their wars with volunteers. The first half of the twentieth century forced a radical revision of those traditional beliefs. Between 1900 and 1945 the United States built a powerful military capable of fighting in almost any corner of the globe. It also joined coalitions and alliances with European powers, forming the foundation for building the most powerful military alliance the world had yet known. The massive changes in the nature of American military power from 1900 to 1945 thus represent not an evolutionary shift, but a revolutionary one.