The counterweight trebuchet is a type of catapult that uses gravity. Early crew-served weapons were siege weapons, like the ballista, trebuchet, and battering ram. Among the most common were the ballista, mangonel and trebuchet. The citadel was bombarded by trebuchet and cannon. Warring States siege equipment consisted of siege ladders, siege towers, and the traction trebuchet. By the 1230s the counterweight trebuchet was a common item in siege warfare. The first is the traction trebuchet, or mangonel, which uses manpower to swing the arm. The counterweight trebuchet did not completely replace the traction trebuchet. The use of the counterweight trebuchet by the Mongols proved especially effective. The attempt was reportedly unsuccessful&colon; the first projectile landed on the trebuchet itself, destroying it. The superiority of the counterweight trebuchet was not clear cut. It is named after the trebuchet, a medieval siege engine. Warwolf is believed to have been a large trebuchet, which destroyed the castle's gatehouse. The Romans, however, reportedly used an early form of the trebuchet in their sieges. The Citadel week featuring a trebuchet competition.