What does Judges 9:51 mean?
Shechem has been defeated and utterly destroyed, along with the pagan-worshipping leaders of that city. In His justice, God has used Abimelech to bring down these evil rulers (Judges 9:15; 46–49). Abimelech is now attempting to wipe out the population of another town, Thebez. Scholars believe this town was northeast of Shechem. Abimelech and his men have already captured the city. They control everything except for a tower. The people of the city have fled into this refuge.Towers in this era were often made of stone and could be several stories tall. These were a common defensive choice during this period. Towers were used both for spotting approaching enemies and as a last stronghold if the city was breached. The tower in Thebez is not like the "stronghold" in Shechem. That area was likely underground, and part of a temple complex. This is more of a traditional fortress-type building. This apparently had a flat roof where people could mount a defense. That's a critical part of what happens next (Judges 9:52–53).