Judges 20:38-40

38The men of Israel had arranged a signal with the men in ambush: When they sent up a great cloud of smoke from the city, 39the men of Israel would turn in the battle.

When the Benjamites had begun to strike them down, killing about thirty men of Israel, they said, “They are defeated before us as in the first battle.” 40But when the column of smoke began to go up from the city, the Benjamites looked behind them and saw the whole city going up in smoke.