10th Mountain Division, United States Army | 3,344 followers on LinkedIn. The 10th Mountain Division (Light Infantry) is a light infantry division in the United States Army based at Fort Drum, New York. Designated as a mountain warfare unit, the division is the only one of its size in the US military to receive intense specialized training for fighting in mountainous and arctic conditions. Reactivated again in 1985, the division was designated the 10th Mountain Division (Light Infantry) to historically tie it to the World War II division and to also better describe its modern disposition.