Book excerpt: Much has been written about the exploits of the American Expeditionary Forces, the men and women sent overseas to fight during World War I, but much less is known about the two million who served in the Army without ever setting foot on foreign soil. This book examines the history of depot brigades, development battalions, U.S. Guards units, Students' Army Training Corps, and other "forgotten" troops charged with training soldiers, guarding installations, and performing myriad other duties. It also chronicles the service of men like actor Jimmy Cagney, author F. Scott Fitzgerald, movie director Frank Capra, children's author Ludwig Bemelmans, and the two million others who served in the United States during the war. At the time, many of these men considered themselves unfortunate cast-offs, doomed to spend the war safe at home while their friends served in combat overseas. But, in the end, it was largely because of them that America could field an effective fighting force.