The launching of NOVA's trebuchet showed how powerful it was.

During peacetime, castle commanders used trebuchets to launch roses at ladies during tournaments. But during a siege, these missile launchers were one of the most fearsome weapons of medieval times.

Early trebuchets were powered by muscle, but later versions relied on a huge counterweight that swung a long arm. When the counterweight was dropped, the device launched a missile from a sling at the end of the arm.

Trebuchets could launch missiles hundreds of yards in large, lobbing arcs at or even over a castle wall. The best trebuchets fired stone missiles weighing up to 400 pounds—big enough to do serious damage to a castle wall. Attackers also used them to launch dung or dead animals into the castle with the intention of spreading disease. Sometimes they even shot out the severed heads of enemy soldiers or even messengers who delivered unsatisfactory peace terms.

If a trebuchet was set up too close to a castle, archers would harass its builders with arrows shot from bows or bolts from crossbows. Castle defenders also would try to destroy rising trebuchets with catapults shot from the castle wall or with sneak attacks to burn it down.