In what battle did the United States suffer the most casualties?

The Battle of the Argonne Forest, which took place on September 28, 1918 - November 11, 1918, was the largest and bloodiest battle for the American military during World War I. The American Armies consisted of 1.2 million men, 380 tanks, 840 planes, and 2780 artillery pieces. Total casualties were a staggering 122,063. Of these numbers: 26,277 were killed 95,786 were wounded.

There were a total of 108.347 total casualties in the Battle of The Bulge (Dec.16, 1944 - January 25, 1945 , the largest American land battle in W.W. II. The Battle of Gettysburg (July 1 - July 3, 1863), the largest battle in the American Civil War, had a total of approximately 47,000 casualties, Union and Confederate. The Battle of the Hurtgen Forest (Sept. 19 - Dec. 18, 1944), the longest single battle ever fought by the U.S. Army, had a total of 33,000 casualties.

The Battle of the Argonne Forest was part of the Grand Offensive all along the Western Front. The Allies were looking to break the stalemate that existed since 1914, characterized by the horrors of trench warfare. In the immediate area of the Argonne Forest, the main target was the city of Sedan It's capture would sever the railway line supplying German forces in France and Flanders.

The American attack, assisted by French troops was successful. Although Sedan wasn't captured, the exhausted Germans requested an armistice, which took effect at the 11th hour, on the 11th day, in the 11th month, 1918.