Baj Singh was a descendent of the family of the third Guru, Guru Amardas Ji.
He came from the village of Mirpur. He was given Amrit by Guru Gobind Singh Ji and was a celebrated, brave warrior of the Khalsa. In September 1708, when Guru Gobind Singh Ji invested Banda Bahadur with the authority to wage war against the religious and political tyranny in Panjab, Baj Singh was one of the five de-voted Sikhs the Guru gave to Banda as an advisory council. The other four Sikhs were Binod Singh, Ram Singh, Vijay Singh, and Kahn Singh. Baj Singh’s brother, Ram Singh, was also one of the right hand men of Banda Bahadur.
After a few conquests, Banda attacked Sirhind on May 12, 710 to punish Wazir Khan, the Governor of Sirhind, for his heinous crimes. In this battle Baj Singh faced Suchanand, the chief secretary of the Nawab, while Banda faced Nawab Wazir Khan. Baj Singh fought with such valour and ferocity that Suchanand and his forces were soon vanquished in the battlefield. Baj Singh then joined Banda Singh, and they converged around Wazir Khan. Baj Singh rushed toward Wazir Khan, who then threw a spear at him. Baj Singh caught hold of the spear and flung it back upon Wazir Khan. It struck the fore-head of Wazir Khan’s horse. At this point Wazir Khan discharged an arrow, which struck Baj Singh’s arm, and then rushed at him with his sword. Seeing Baj Singh under attack, Fateh Singh struck his sword with such a force that it cut Wazir Khan from shoulder to waist. Such valour, courage, and skillful wielding of arms by Sikh warriors like Baj Singh won the battle of Sirhind.