If you have a fortification, at a minimum you put the entrance well above ground level and accessed by a bridge or even just a plank and the last thing you do is pull up the drawbridge, pull in the plank, burn the bridge. Beyond that, the castle should have a layered series of defenses where the attackers pounding on the gate have rocks and burning oil dropped on them from the overhanging battlements and “murder holes.” Ideally that is just the outer layer, and that the real entrance is offset some distance so attacker must traverse a gauntlet between the inner and outer walls.
