Meuse–Argonne offensive

The Meuse–Argonne offensive was a major part of the final Allied offensive of World War I that stretched along the entire Western Front. It was fought from September 26, 1918, until the Armistice of November 11, 1918, a total of 47 days. The Meuse–Argonne offensive was the largest in United States military history, involving 1.2 million American soldiers. It is also the deadliest battle in the history of the United States Army, resulting in over 350,000 casualties, including 28,000 German lives, 26,277 American lives and an unknown number of French lives. American losses were worsened by the inexperience of many of the troops, the tactics used during the early phases of the operation and the widespread onset of the global influenza outbreak called the "Spanish flu".

Wikipedia