Abimelech chased him... — He won a complete victory; but Gaal and his forces were able to secure themselves in Shechem. They succeeded in closing the gates against Abimelech, but only at the cost of many lives.
Related Commentaries of Judges 9:40
Judges 9:40
40 And Abimelech chased him, and he fled before him, and many were overthrown and wounded, even unto the entering of the gate.