He was born a commoner in Gujranwala, in a Muhiyal family belonging to the Ambral branch of the Bali Clan. He was the grandson of Himmat Singh Bali, and his father Daata Ram was a counselor to Sultan Mukkarb Khan, the Gakhar Subedar of Gujrat.
He was conferred by Maharaja Ranjit Singh the title of Raja for his conquests of Haripur, Nowshehra and Peshawar. The town of Mansehra derives its name from him. Military career and later While in Lahore in search of a job, he happened to participate in a hunting expedition of Maharaja Ranjit Singh, in which he caught the notice of the latter by single-handedly killing a leopard with his sword.
Impressed by his valor, the Maharaja had him inducted into the army under the famous General Hari Singh Nalwa.
Mahan Singh played a key role in the battles of Peshawar and Kashmir, and in the 1818 siege of Multan, was seriously wounded two times. He went on to become second-in-command to Hari Singh Nalwa.
In April 1837, he was the main defender of the Jamrud Fort, holding out against an invasion by Afghans. In the subsequent battle, Hari Singh Nalwa was done to death but Mahan Singh maintained the news secret until reinforcements arrived from Lahore.
