Tipu Sultan's father had expanded on Mysore's use of rocketry, making critical innovations in the rockets themselves and the military logistics of their use. He deployed as many as 1,200 specialised troops in his army to operate rocket launchers. These men were skilled in operating the weapons and were trained to launch their rockets at an angle calculated from the diameter of the cylinder and the distance to the target. The rockets had twin side sharpened blades mounted on them, and when fired "en masse", spun and wreaked significant damage against a large army. Tipu greatly expanded the use of rockets after Hyder's death, deploying as many as 5,000 rocketeers at a time. The rockets deployed by Tipu during the Battle of Pollilur were much more advanced than those the British East India Company had previously seen, chiefly because of the use of iron tubes for holding the propellant; this enabled higher thrust and longer range for the missiles (up to 2 km range).