The American Expeditionary Force in WWI
When the United States entered World War I in 1917, the outcome of the conflict remained uncertain. After three years of brutal fighting, the Allied powers—France, Britain, and Russia—were exhausted and struggling to maintain momentum against German forces.
The arrival of fresh American troops, known collectively as the American Expeditionary Force (AEF), helped to tip the balance. Under the command of General John J. Pershing, U.S. soldiers brought new energy, manpower, and resources to a war that had long since settled into bloody stalemate. Though the AEF joined the war late, its impact was significant. Through its involvement in major offensives and critical battles, the U.S. played a decisive role in the final year of fighting and helped secure an Allied victory.
Building the AEF
When Congress declared war on Germany in April 1917, the United States had a relatively small army compared to the massive forces already deployed in Europe. The government quickly instituted a draft to raise troops and began preparing them for overseas service. By the end of the war, over two million American soldiers had served in Europe.
These troops were organized into the American Expeditionary Force, a new and independent military force that would not be folded into British or French command. General John J. Pershing, chosen to lead the AEF, insisted that American troops fight under U.S. leadership. He believed this approach would boost morale, protect national interests, and give the U.S. a clear role in peace negotiations. Pershing’s leadership was firm, strategic, and deeply committed to establishing the United States as a serious military power on the world stage.
Turning the Tide: U.S. in Key Battles
The AEF first entered combat in early 1918, providing reinforcements and relieving exhausted Allied units. Over the course of that year, American troops took part in several critical operations that helped shift the momentum of the war.
One of the first major battles involving U.S. forces was the Second Battle of the Marne in July 1918. German forces had launched a major offensive in an effort to break through Allied lines before American reinforcements could arrive in full force. With the help of fresh U.S. troops, the Allies halted the German advance and launched a counterattack that pushed enemy forces back. The battle was seen as a turning point—it was the last major German offensive on the Western Front.
Next came the Battle of St. Mihiel, the first major offensive planned and led entirely by American forces. More than 500,000 U.S. troops participated, and in just four days, they forced a German withdrawal from a strongly fortified position in northeastern France. The victory at St. Mihiel boosted Allied morale and proved that American forces could operate effectively on their own.
The largest and most grueling battle for the AEF was the Meuse-Argonne Offensive, launched in September 1918. It involved over a million American soldiers and lasted for six weeks. The objective was to break through German defensive lines and cut off supply routes. The terrain was difficult, and casualties were high, but the offensive succeeded in pushing German forces back and accelerating the end of the war. The Meuse-Argonne campaign remains the largest and deadliest battle in U.S. military history.
Heroes and Homegrown Contributions
Among the most celebrated individuals of the AEF was Alvin C. York, a soldier from Tennessee who became a national hero for his actions during the Meuse-Argonne Offensive. Despite having initially registered as a conscientious objector due to his religious beliefs, York ultimately served and distinguished himself in battle. He reportedly captured over 130 German soldiers almost single-handedly, an act that earned him the Medal of Honor and symbolized American bravery and effectiveness.
Another vital contribution came from Alabama’s own 167th Infantry Regiment, part of the famous “Rainbow Division.” These National Guard troops were among the first Americans to see combat in France. Their courage and sacrifice, particularly in the Champagne and Meuse-Argonne sectors, reflected the nationwide commitment to the war effort—even among those from rural or Southern states who had never seen combat before.
Significance of the AEF
Though American involvement in World War I lasted only about 18 months, the impact of the AEF was far-reaching. The arrival of U.S. troops gave the Allies a psychological and strategic edge. American soldiers helped fill exhausted ranks, lifted morale, and added critical manpower at a time when Germany could no longer match the numbers.
Equally important, the AEF established the United States as a modern military power. It demonstrated that the U.S. could raise, train, and deploy a large army quickly—and do so with professionalism and coordination. The insistence on independent American command also allowed the U.S. to influence the terms of peace and play a major role in postwar diplomacy.
World War I was a brutal conflict, and the cost was high: more than 50,000 American soldiers died in combat, and many more were wounded or fell victim to disease. But the legacy of the AEF lives on. Its success helped end the war, redefined U.S. military strategy, and marked the emergence of the United States as a central figure in global affairs.