Sketch of an infantry attack in woods at Argonne front by Lucien Jonas. The Battle of the Argonne Forest, was a part of the final Allied offensive of WWI that stretched along the entire Western Front. It was fought from September 26, 1918, until the Armistice on November 11, a total of 47 days. The battle was the largest in United States military history, involving 1.2 million American soldiers, and was one of a series of Allied attacks known as the Hundred Days Offensive, which brought the war to an end. The Meuse-Argonne was the principal engagement of the American Expeditionary Forces during WWI.