Manohar Singh, son of Mathura Singh was born in 1895. He was a reputed businessman in Aberdeen Bazaar. He was an active member of the Indian Independence League.
In March 1942 during the Second World War, the Japanese occupied the Andaman Islands. In the same year in April, the Andaman branch of the Indian Independence League was formed following the path of Rash Behari Bose. Manohar Singh joined the League and contributed liberally to the strengthening of the League and its expansion.
He and other members actively took part in activities of the League with the objectives of organizing, strengthening, and collecting funds for the League. The League members motivated the people through extensive public meetings, cultural shows, patriotic songs, dramas, etc. These activities helped in uniting the islanders and igniting in their a strong sense of nationalism against British imperialism. Under the Indian Independence League, formed different sister branches such as Sewa Samiti, Cultural Wing, and Peace Committee.
Manohar Singh was one of the leading members to play an active role in the expansion of the League involving a large number of people from villages.
Netaji Subhas Chandra Bose visited the Andaman Islands on 29 December 1943. On his arrival at the Lamba Line Airport of Port Blair, members of IIL and INA received him solemnly. Netaji hoisted the Indian flag on 30 December 1943 for the first time at Gymkhana Ground at Port Blair. On 31 December, he visited the Headquarters of the League. All the League members including Manohar Singh were actively engaged in the management of functions during the visit of Netaji. After his departure on 31 December, the members of the Indian Independence League came to target the Japanese.
In January 1944, Manohar Singh and many other members of the Indian Independence League were arrested and incarcerated in the Cellular Jail. He was brutally tortured to confess that he was a British Spy, but he did not accept the false allegation. He was released after a week.