‘And Abimelech, and the companies that were with him, rushed forward, and stood in the entering of the gate of the city, and the two other companies ran on all the people that were in the field and smote them.'
This now explains the attack in more detail, as commonly happens in ancient writings. Before attacking the people, now out in the countryside, they seized the gates to prevent them being closed against them, and then two of the companies smote the people outside, while the third held the gate.