In December 1798 he was appointed by Lord Mornington, the governor-general, to command the field army which was intended to attack Tipu Sultan, and in a few months of campaigning Harris reduced the Kingdom of Mysore and stormed the great stronghold of Seringapatam, where the Tipu died in its defence.
These engineer troops fought in numerous campaigns in India at Sholinghur, Seringapatam, Assaye (along with Major General Arthur Wellesley, later Duke of Wellington, and also in Egypt, China, Burma and other places abroad.
The Seringapatam medal (Sri Ranga Pattana - ಶ್ರೀರಂಗಪಟ್ಟಣ), commissioned by the East India Company in 1801, was a Conrad Heinrich-designed military medal distributed to those soldiers who contributed to the British victory in the 1799 Battle of Seringapatam against the armies of Tipu Sultan, ruler of the southern India in the Kingdom of Mysore.