During the Indian Peacekeeping Forces' (IPKF) mission in Sri Lanka, on 29 July 1989, an ambush was planned to eliminate militants in Tanniyuttu town of Sri Lanka. 

Rifleman Mohan Singh was light machine-gunner during the ambush and very soon, they came in contact with a large group of around 60 to 80 terrorists. 

The brave rifleman responded immediately and engaged the militants effectively. While firing, he suddenly observed a group of militants rushing to the neighbouring section to snatch the weapons from the injured soldiers. Without caring for his personal safety and with tremendous courage, he rushed with his light machine gun and unleashed heavy fire on the militants, inflicting heavy casualties on them.
During the fierce gunfight, Rifleman Singh sustained bullet injuries and made the supreme sacrifice, while saving his fellow soldiers. He was awarded the Vir Chakra posthumously for his gallantry and heroism.