What does Judges 9:52 mean?

Abimelech is attempting to defeat the people of a town called Thebez and take control of their city. He and his men have successfully breached the gates and walls. They control every part of the town except for the tower (Judges 9:50–51). Thebez is said to have an especially strong tower with a flat roof. The people of the city have fled into the tower, barricaded themselves inside, and have gathered on the roof.

It's not clear if Abimelech's plan is meant to duplicate what he did in Shechem: to burn his enemies alive (Judges 9:48–49). Since this is likely a stone tower, with a wooden door, he may simply be trying to burn the door and gain access. If so, Abimelech and his men will have to fight their way up the tower from the inside once they gain access.

Of course, one advantage of defensive towers is high ground. The top level of these structures might be several stories high. To attack, an enemy must come within range of weapons that can be thrown down from above. Abimelech attempts to get close enough to burn the door. That will bring him within the range of enemy attack.