Judges 20:40 (KJV)

Now there was an appointed sign between the men of Israel and the liers in wait, that they should make a great flame with smoke rise up out of the city.

And when the men of Israel retired in the battle, Benjamin began to smite and kill of the men of Israel about thirty persons: for they said, Surely they are smitten down before us, as in the first battle.

But when the flame began to arise up out of the city with a pillar of smoke, the Benjamites looked behind them, and, behold, the flame of the city ascended up to heaven.

And when the men of Israel turned again, the men of Benjamin were amazed: for they saw that evil was come upon them.

Therefore they turned their backs before the men of Israel unto the way of the wilderness; but the battle overtook them; and them which came out of the cities they destroyed in the midst of them.