Ballistas or springalds were siege engines that worked on the same principles as crossbows. With their origins in Ancient Greece, tension was used to project a bolt or javelin. Missiles fired from these engines had a lower trajectory than trebuchets or mangonels and were more accurate. They were more commonly used against the garrison rather than the buildings of a castle. Eventually cannons developed to the point where they were more powerful and had a greater range than the trebuchet, and became the main weapon in siege warfare.