The word "engineer" entered the English language in the carly 1300s. It denoted a person who built military engines, also known as siege engines. These were various machines used to lay siege to a walled city, castle, or fortress. Siege engines included things like battering rams, ballistas (giant crossbows), and catapults. Although military engines got their start around 400 BCE with the Greeks and Romans, we tend to think of siege weapons being unleashed upon castles in medieval battles. This explains the timing of the introduction of the word "engineer." At that time, two types of catapults were popular: the mangonel and the trebuchet. The mangonel relied on a torsion device to store energy, while the trebuchet relied on a weighted arm. The trebuchet in particular was quite powerful, able to sling stones weighing 300 pounds (136 kg) or more at castle walls to crush them. The range was hundreds of yards. When not shooting projectiles, catapults could fire incendiaries, animal carcasses, or diseased human bodies. The basic mechanics of both catapult designs are straightforward. A trebuchet stores energy in the rise of a heavy weight attached to a long arm. In a big trebuchet, the arm might be 60 feet (18 meters) long and the weight could be as heavy as 10 or 12 tons. The mangonel used hundreds of tightly twisted rope strands. Cocking the catapult involves pulling the arm down 90 degrees, adding even more torsion to the ropes. When released, the ropes would spring back to launch the projectile. In 1304, engineers built what is believed to be the largest trebuchet ever for a siege that was taking place in Scotland. The trebuchet's name was War Wolf. By repeatedly launching projectiles weighing 300 pounds (136 kg), one of the walls at Stirling Castle crumbled. Engineers won the battle by using mechanical engineering to crush heavily fortified stone walls.