Joshua 8:14-18

And it came about, when the king of Ai saw them, that the men of the city hurried and got up early, and went out to meet Israel in battle, he and all his people at the appointed place before the desert plain. But he did not know that there was an ambush against him behind the city.

Then Joshua and all Israel pretended to be defeated before them, and fled by the way of the wilderness.

And all the people who were in the city were called together to pursue them, and they pursued Joshua and were lured away from the city.

So not a man was left in Ai or Bethel, but they had all gone out after Israel, and they left the city unguarded and pursued Israel.

Then the Lord said to Joshua, “Reach out with the sword that is in your hand toward Ai, for I will hand it over to you.” So Joshua reached out with the sword that was in his hand toward the city.