In the Spring of 1918, Germany launched its last major effort of the war, a series of offensives along the Western Front. Although initially the Allies were forced back, they recovered and prevented the Germans from breaking through. During these battles, large numbers of American troops entered combat for the first time. These actions taught U.S. troops and their commanders costly but valuable lessons, and proved that Americans were ready to play a major role in the final push to end the war.
By March 1918, there were over 300,000 American troops in France. A few units had been called into action during the Battle of Cambrai in November 1917, but the vast majority of U.S. troops had yet to see combat. In keeping with Commanding General John J. Pershing's plan to organize and deploy an independent American army, most of them were training in rear areas, or assigned to relatively quiet sections of the Allied lines.
The British and French were still recovering from setbacks they had suffered in 1917, and were simply holding on until the Americans were ready. Meanwhile, Germany had quietly moved hundreds of thousands of soldiers to the Western Front -- forces that had been freed up by Russia's departure from the war and a major German victory on the Italian front.
On March 21, the reinforced German armies attacked. They used new tactics that relied on speed and surprise, rather than the enormous week-long artillery barrages and mass frontal assaults of the past. Short, intense artillery bombardments blasted gaps in the Allied lines that were exploited by specially trained and equipped shock troops. These "stormtroopers" bypassed strong points and moved quickly forward, opening the way for larger units to follow.
At first, the Germans made good progress, advancing deep into Allied territory. However, the battered British and French troops held, and the German attacks ground to a halt without achieving their objectives. A follow-up offensive in Flanders, to the north, resulted in a similar outcome.
At first, American forces took little part in these battles. However, as the German offensives continued, Pershing agreed to send individual U.S. units to fight under French or British command. In late May, a U.S. regiment successfully seized the village of Cantigny, in the first U.S. attack of the war. Although the action was relatively minor, it was an important step forward for American troops.
A few days later, U.S. forces moved to reinforce Allied positions in the Chemin des Dames area northeast of Paris, where they prevented the Germans from crossing the Marne River to threaten the French capital. To the west, U.S. Marines halted the German advance at Belleau Wood. After three weeks of costly fighting, the Marines retook the wood, proving that American fighting men were capable of standing toe-to-toe with the battle-hardened Germans.
The Germans launched their last assault, which they optimistically named Den Friedensturm (peace offensive), just to the east of their previous effort. As before, they achieved initial successes, advancing over the Marne River near the town of Chateau-Thierry. Once again, French and American forces rallied to stop the German advance. Over 85,000 U.S. troops saw action during this engagement -- the largest number of Americans in combat since the Civil War. The failure of this final offensive definitively ended German hopes of winning the war.
As the last German attack stalled, the Allies launched a major counter-offensive along the Aisne and Marne rivers. For the first time, multiple American divisions fought shoulder-to-shoulder, sending 270,000 U.S. troops to push the Germans back. Two newly-formed American corps led much of the advance, inspiring further Allied confidence in U.S. troops and leadership. In August, the advance ran its course, and the Allies paused to regroup.
The performance of U.S. forces in the Aisne-Marne Offensive proved that the Americans were ready to take on a full share of the upcoming fighting. The various units that had been placed under Allied command during the German offensives were brought back under American control, and the First United States Army was officially formed on July 24th, with Pershing as its commander.
When the Germans had resumed unrestricted submarine warfare in early 1917, they had gambled that they could defeat the Allies before the Americans could raise, ship over, and train an effective fighting force. The birth of the First U.S. Army meant that they had lost this gamble. Over one million American troops now stood ready for the final Allied push to end the war.