Castles are probably the most famous invention of the Middle Ages. Their design took tremendous ingenuity, making them deadly to attackers and immensely difficult to take. Because of this, attacking armies had to be even more ingenious…. A good way of overcoming these defences was through mining. Attackers would dig a tunnel underground up to the castle walls causing them to crumble and collapse. At the Siege of Rochester in 1215, King John found a cunning, albeit cruel, way of doing this. By burning the fat from 40 pigs, which one source claims were 'too fat to eat’, his men brought down the entire south-east corner of the keep! Machines such as trebuchets were the heavy artillery of the pre-gunpowder era. They could hurl massive projectiles with remarkable accuracy from up to 400 metres away. A trebuchet consists of a long beam attached to a pivot rod on a heavy frame. A counterweight was placed on one end of the beam and a sling attached to the other. The sling, with a missile in it, would be whipped skyward and towards the target. Trebuchets were used to deadly effect during the Siege of Kenilworth Castle in 1266. They could also be used alongside mining. At the Siege of Dover in 1216, Prince Louis of France used both two tactics together to assault the castle gateway, allowing his forces to pour through an opening, take the barbican and kill its commander. Although medieval warfare was horrific and brutal, it promoted ingenuity and led to remarkable technological innovation.