By 1918, the Selective Service Act, the conscription of young men into the US army, meant that the relatively small standing army swelled to 4,000,000. General Pershing, the commander of the American Expeditionary Force (AEF), insisted troops receive full combat training before arriving in France, so their direct impact on the conflict was limited until spring 1918. However, the steady influx of American troops, reaching a rate of 10,000 per day, had a critical impact on German strategy. The end of the war on the eastern front freed 50 German Divisions for redeployment in the west. This offered a window of opportunity before full American deployment was achieved, so German High Command gambled on an all-out offensive in March. Once this attack had been weathered, American reinforcements and equipment played a major role in the counteroffensive that ended the war: in total, 1.2 million American troops participated in the Meuse-Argonne Offensive.
— OR —