Babur had invaded India in 1526 and used brass cannons in the First Battle of Panipat, for the first time in this part of the world. This was the time when Hemu, who was dealing in food items till then, set up brass foundries to manufacture cannons in Rewari, to make supplies to the then Indian ruler Sher Shah Suri with whom he had close contacts. Hemu took technological help from Portuguese in manufacturing brass cannons and production of saltpetre used to make gunpowder. With the help of these supplies of brass cannons and saltpetre, that Sher Shah Suri could defeat Babur's son Humanyun in 1539, and force him to retreat to Kabul. Brass cannons had become an all-important war tool by that time.