When the Congress declared war on Germany and the other Central Powers on 6 April 1917, America’s Army was ill-prepared to fight what would later be called the “Great War.” After all, the entire Army consisted of 125,000 Regular Army Soldiers and 67,000 National Guardsmen along the Mexican border. Moreover, the Army was built around regiments; larger units such as divisions, corps, and armies existed only on paper. But, by the time what we now call World War I ended, on 11 November 1918—just nineteen months later—the Army had grown to 3.7 million, with two million men serving in the American Expeditionary Force (AEF) in France.