Answer:
Step-by-step explanation:
Height: Its height and width make it very solid and this prevented any enemies from intruding. Most sections of the Great Wall were built on mountain ridges. This would exhaust an enemy army's effective strength by the time they reached the wall.
Watchtowers: Soldiers at neighboring towers could see the smoke/fire during the day/ night, alerting the troops that the enemy was coming and a battle was about to start.
Passes: Once the enemies approached, the soldiers stationed in the passes could come to the battle site via the wall after seeing the messages from the beacon towers.
Internal Stairways: The Jiankou section of the Great Wall has the dangerous sky stair. The angle of ascent is between 70 and 80 degrees. The Simatai section has the ladder-like 'Stairway to Heaven', an 85 degree slope which narrows to 30 centimeters wide in some places. Thousands of battles have been fought at the Great Wall.
I hope i helped!