The next day the people of Shechem went out to the fields to work. Abimelech found out about that.
Then Abimelech returned to the city of Arumah. Zebul forced Gaal and his brothers to leave the city of Shechem.
So Abimelech separated his men into three groups. He wanted to attack the people of Shechem by surprise. So he hid his men in the fields. When he saw the people coming out of the city he jumped up and attacked them.