By 1915 the western front had become bogged down in trench warfare, and within two years the Allied position was becoming increasing tenuous as British, Italian, and French forces sustained massive casualties, mutinies broke out in the French army, and revolutionary forces successfully overthrew the czar in Russia. In April 1917 the Allies' hope was renewed after the United States committed the American Expeditionary Forces (AEF) to the fight, but by the time most of those troops arrived a year later, Britain and France had sustained hundreds of thousands of casulties in four years of brutal trench warfare.

The "Yanks" Arrive.

By 1918 the U.S. Army had been expanded into a force of 3.7 million soldiers in sixty-two divisions of 28,000 men. Forty-two of these divisions were deployed to Europe, and within a little more than six months after the first U.S...