On 8 December 1941, the day after the Japaneseattack on Pearl Harbor, the army activated its first mountain unit, the 87th Mountain Infantry Battalion (which was later expanded to the 87th Infantry Regiment) at Fort Lewis, Washington, south of Tacoma. It was the first mountain warfare unit in U.S. military history
The 10th Light Division (Alpine) was constituted on 10 July 1943 and activated five days later at Camp Hale under the command of Brigadier General Lloyd E. Jones.
On 6 November 1944, the 10th Division was redesignated the 10th Mountain Division