Whenever we watch shows on olden warfare where people are still using horses, swords and arrows, we will see the attackers trying to climb up the wall and some others trying to bang open the wooden door with a huge wood log or metal log.
The defenders will shoot arrows down and throw rocks down from the wall at the attackers and a small group of defeneders will stand behind the wooden door trying to stop the attackers from breaking open the door but eventually the attackers will break open the door and rush into the city to attack them.
I always wonder why is it the defenders do not use a very simple and effective method of putting many big rocks behind the wooden door.
This will make it very difficult for the attackers to break open the door.
Even if they break open the door, they will still need a long time to push away all the rocks before their troops can enter.
The defenders should stand behind these rocks so that any attackers who try to climb over the rocks, the defenders can easily stab them from near or shoot arrows at them from far.
In this way, it is almost impossible for the attackers to enter through the wooden door.
The only way is for them to try to climb up the wall using ladders which is very difficult as the defending soliders can shoot arrows down, throw stones down, pour oil down and than burn them, push away the ladders letting them fall down to their death etc