Why was difficult to attack a castle

Why was difficult to attack a castle?

During the Medieval period, castle became important. These huge castles were mostly invented for defending the foreigner attacks. The castles were also the sin of the noble and royal power. Eventually, there were various kinds of castle, but most of the castles were used for protecting and defending during siege warfare. While the builders built these castles, they added much prevention structures to the castles, those preventions made the castles difficult to attack.

Constructions of the castle to defense
Castles defensed by deep moats and the surrounding concrete walls, which could prevent from the enemies. The moat can be easily cross by those attackers, but it decreased the risk of tunneling under the castle. The walls that surround the castle were extremely high. Thus, the high walls prevented the invaders to climb over the walls. Tall and concrete curtain walls were also surrounded the castle interior, they acted as the solid shield of the castles. Throughout the curtain walls, flanking towers were combined within the walls. The flanking towers made the castle more difficult to seize. At the top of the walls were the tooth shaped battlements where the defenders could fire missiles through the crenels, which were the gaps between. Merlons, the raised parts between were used to shelter the defenders from the attacks. Along the walls, there were the entrances, the gate door. To fully defend the attackers, the gate door was made by a lot of elements. The first element was gate door itself, the massive wooden door that was bolted with wooden beams to support the door and avoided the entrance of the attackers. The wooden bolts made the door hard to batter by battering ramps to vanquish the door. If the door was smashed down, portcullis, a gate made by wood and combined with nails and irons will drop down. The metal will hammer onto the gate to add strength to the gate. There were also machicolations, which were the