Hoon joined the Indian Military Academy in Dehradun in 1947. He was commissioned in Sikh Regiment and posted in Kashmir in various sectors from 1949 to 1961. He was posted at the Barahoti post during the 1962 Indo-China War. In 1965, during the Indo-Pakistan War, he fought in the Punjab, Sialkot and Pasrur sectors. He was promoted to the post of Lieutenant Colonel and moved to Kargil sector in charge of Special Mountain Forces. In 1970, he was promoted to Brigadier and appointed to lead the Sikkim Brigade deployed at Nathu La. He was later posted at Hussainiwala in the Ferozpur sector in Punjab in 1974. He was made the Chief of staff of the Strike Corps in Chandimandir in 1980. He led the 13th Battalion of the Dogra Regiment.