A man named Gaal, a fairly recent newcomer to the town of Shechem, boasted during a drunken pagan feast that if elected in Abimelek's place he would return the region to the glory it had during the reign of its founder, Hamor. He promised to reinstate the policies and prosperity of that era. While deep in his cups, as the saying goes, he boasted that if given a chance he will remove Abimelek from power himself: "If only this people were under my command! Then I would get rid of him. I would say to Abimelek, 'Call out your whole army!'" (Judges 9:29)
He's going to get an opportunity to face down Abimelek, and sooner than he thinks, for Zebul (whom we were told yesterday is Abimelek's deputy) hears about Gaal's boasting and recognizes him as a threat to Abimelek's government. "When Zebul the governor of the city heard what Gaal son of Ebed said, he was very angry. Under cover he sent messengers to Abimelek, saying, 'Gaal son of Ebed and his clan have come to Shechem and are stirring up the city against you. Now then, during the night you and your men should come and lie in wait in the fields. In the morning at sunrise, advance against the city. When Gaal and his men come against you, seize the opportunity to attack them.'" (Judges 9:30-32)
Zebul knows Gaal and his men won't be in good fighting condition at sunrise. They will be partying hardy all night, celebrating the grape harvest at the temple of their false god. By the early morning hours they'll be suffering the effects of too much alcohol and too much rich food. According to the National Institute On Alcohol Abuse And Alcoholism, a hangover can include some or all of the following symptoms: fatigue, weakness, thirst, headache, muscle aches, nausea, stomach pain, vertigo, sensitivity to light and sound, anxiety, irritability, sweating, and increased blood pressure. Gaal isn't going to have himself a first-rate army in the morning, not by a long shot.
"So Abimelek and his troops set out by night and took up concealed positions near Shechem in four companies." (Judges 9:34) It would appear that Zebul, Abimelek, and all these men are sober during this night. They have evidently not participated in the revelries common to grape harvest season but have kept their wits about them. This gives them an advantage over Gaal and his men.
Gaal doesn't know Zebul has warned Abimelek. Because he sent messengers to Abimelek instead of going himself, he is present in the morning to try to convince the bleary-eyed, hungover Gaal that he isn't really seeing what he thinks he's seeing. "Now Gaal son of Ebed had gone out and was standing at the entrance of the city gate just as Abimelek and his troops came out from their hiding place. When Gaal saw them, he said to Zebul, 'Look, people are coming down from the tops of the mountains!' Zebul replied, 'You mistake the shadows of the mountains for men.'" (Judges 9:35-36) The sun probably hasn't made its appearance over the hills yet but there's enough light in the sky to cast shadows. Zebul causes Gaal to waste precious time by causing him to doubt whether the shadowy movements he's seeing are actually soldiers or just a trick of the light.
I picture Gaal rubbing his dry, gritty eyes and squinting again toward the area where he thought he saw men approaching. As the morning grows ever lighter, he realizes he was correct and that Zebul is trying to keep him from mounting a defense. "But Gaal spoke up again: 'Look, people are coming down from the central hill, and a company is coming from the direction of the diviner's tree.'" (Judges 9:37)
The ruse is exposed but by this time it doesn't matter. Abimelek and his men have almost reached the city. Zebul stops trying to convince Gaal his eyes are deceiving him and begins to taunt him instead. "Then Zebul said to him, 'Where is your big talk now, you who said, 'Who is Abimelek that we should be subject to him?' Aren't these the men you ridiculed? Go out and fight them!'" (Judges 9:38) Zebul is saying something like, "Don't be all talk and no action. You said this was what you wanted. Well, here's your chance! Get on with it if you think you can do it!"
"So Gaal led out all the citizens of Shechem and fought Abimelek. Abimelek chased him all the way to the entrance to the gate, and many were killed as they fled. Then Abimelek stayed in Arumah, and Zebul drove Gaal and his clan out of Shechem." (Judges 9:39-41) This is the last we'll hear of Gaal and it's a good thing Abimelek and Zebul and their soldiers were able to drive him and his clan from the region. If they had not, he would have taken Abimelek's place and would probably have been more wicked and ruthless than Abimelek himself. He might have attained more power within the borders of Israel than Abimelek ever did.
Abimelek is in a position to rule unopposed now. The remaining men of Shechem and of the surrounding area might have put their support behind him again, not necessarily because they want him reigning over them but because it's in their best interests (personally and politically) to give him their allegiance. But he can't forgive their treachery. He can't forget that they betrayed him---one of their own townspeople---in favor of that upstart Gaal who was an outsider. In tomorrow's study he'll take steps to avenge his wounded pride and this will accomplish what Gaal's attempt to dethrone him did not. Abimelek will bring about his own demise by his own vindictive actions.