The Light Division were a division within the British Army.
In an alternate timeline, this division served in the Crimean War for the British Empire against the Sontarans of Sontar. They were led by Lieutenant General Logan. Mary Seacole setup a hotel and nursing station for the soldiers near Sevastopol to allow them a place to rest between battles against Commander Skaak's army. Logan led his men in a costly battle against Skaak's soldiers in 1855.
With the Thirteenth Doctor's help, Logan and Seacole were able to tamper with the Sontaran's fuel, making them unable to inhabit Earth's atmosphere. However, Logan proceeded to kill the Sontarans by igniting barrels of gunpowder, setting the Sontaran's encampment in flames. (TV: War of the Sontarans)