A siege is a technique for invading castles. Most of the time the physical attacks had enough force that the people who are being attacked would surrender. Sometimes their lord would call the surrender, but most of the time the people in the castle would be ready for the siege. Another way a siege was used was the people who are attacking would surround the castle and not let the attacked come out so they would starve. The people would wait for them to come out for months and maybe years.
A Ballista is a giant crossbow or a type of catapult. It takes a long time to load up. They used it for long range attacks in war. The Ballista was also created in ancient Greece. The Ballista is still used today. The Ballista was very a common weapon. You mostly see the Ballista in museums We are lucky we don't live in the medieval times cause can you imagine being shot by a type of catapult? The Ballista was made in four hundred BC in ancient Greece. The Romans took over the Ballista so the could use it in wars.