Subedar Sujjan Singh was fascinated by the army life and soon joined the army before completing his school education. He was recruited into the 13th battalion of the Kumaon Regiment, a regiment known for its gallant soldiers and various battle exploits. During 1971 Indo-Pak war, he along with his unit was deployed in the Longewala region in Rajasthan and the unit received the theater honour for its valour and service.