In 1839, he was sent to Peshawar with other army generals to help Colonel Wade`s contingent to force the Khaibar Pass for an invasion of Afghanistan. Tej Singh acquired great influence over Kanvar Nau Nihal Singh. He supported the cause of Rani Chand Kaur, when, after the death of Nau Nihal Singh, she staked her claim to regency. He was among those who signed the agreement of 27 November 1840 proclaiming Chand Kaur as Regent. On the eve of the AngloSikh war of 1845-46, Tej Singh was appointed commanderin chief of the Sikh army. His conduct during this war and during the one following was however marked by duplicity.
He established secret liaison with the British and desired their victory rather than that of the army he led. Two divisions under his command hovered around Firozpur when that strategic town could have been stormed and the small British garrison destroyed. At the fiercely fought battle of Ferozeshah (21 December.1845), he kept his army away from the battlefield. When the action was over, he appeared with his army on the morning of 22 December and drove straight into the shattered British cavalry lines. But suddenly his guns ceased to fire. He abandoned the field and took the road to Lahore.
At Sabhraon (10 Feburary 1846), he advised the brave Sikh general, Sham Singh Atarivala, to leave the battlefield. The latter continued the battle determined to fight to the end, but Tej Singh and Commander Lal Singh fled hastily even as the contest hung in the balance. As the batde went in favour of the British, Tej Singh cut out the retreat of the Sikh army by sinking the bridge of boats and the tete de pont constructed in front of it. At die end of the war, he made an offer of Rs. 25,00,000 to Lord Hardinge to buy for himself an independent kingdom like Gulab Singh had done. However, he retained his position of preeminence in the new setup.
He was nominated president of the council of Regency in December 1846, and was allowed to continue as commanderin chief of the Sikh army. He was created Raja of Sialkot in August 1847. At the time of the annexation of the Punjab to Britain, he was guaranteed the enjoyment of all the privileges and rights which he possessed under the Sikh government. He was invested with the full powers of a magistrate in his estate and was nominated a member of the committee for the management of the Golden Temple.
During the uprising of 1857, he raised Sikh cavalry regiments to aid the British. His scattered jagirs were consolidated and he received the new title Raja of Batata. He died on 4 December 1862 and was succeeded by his adopted son Harbans Singh (his brother whom he had adopted before the birth of his son, Narindar Singh).
1. Suri, Sohan Lal, `Umdat ut-Twarikh, Lahore, 1885-89
2. Griffin, Lepel, The Punjab Chiefs. Lahore, 1890
3. Hasrat, Bikrama Jit, Anglo-Sikh Relations. Hoshiarpur, 1968
4. Chopra, Barkat Rai, Kingdom of the Punjab. Hoshiarpur, 1969
5. Harbans Singh, The Heritage of the Sikhs. Delhi, 1983