Judges 20:38-40

38The Israelites had arranged with the ambush that they should send up a great cloud of smoke from the city,

39and then the Israelites would counterattack. The Benjamites had begun to inflict casualties on the Israelites (about thirty), and they said, “We are defeating them as in the first battle.”

40But when the column of smoke began to rise from the city, the Benjamites turned and saw the whole city going up in smoke.