[2] In June 1844 Renny was commissioned second lieutenant in the Bengal Horse Artillery, taking part in the First Sikh War, including the battle of Sobraon on 10 February 1846.

Siege guns had been brought into the city and began battering a breach in the repaired walls of the arsenal allowing the 61st Regiment and the Baluchi Battalion to storm the building.

With musket balls cracking around him and in imminent danger of being blown apart, Second Lieutenant Edward Thackeray of the Bengal Engineers extinguished the blaze.

Simultaneously, Lieutenant George Renny of the Bengal Horse Artillery climbed the arsenal's wall and flung several shells with lighted fuses into the midst of the attackers.

Early in the forenoon of that day, a vigorous attack was made on the post by the enemy, and was kept up with great force for some time, without the slightest chance of success.

The roof having been again set on fire, Captain Renny with great gallantry mounted to the top of the wall of the magazine, and flung several shells with lighted fuzes over into the midst of the enemy, which had an almost immediate effect, as the attack at once became feeble at that point, and soon after ceased there.