Joshua 8:17

There was not a man left in Ai or Beth-el. — Another singular justification of the peculiar strategy of Joshua. The road past Beth-el to Ai had been left open. It passes the north end of the two ravines in which Joshua’s ambush was posted. At the same time, it would have been easy to conceal a chain of sentinels that could observe it and tell the 35,000 men in ambush what was going on, so that if any attempt had been made by the men of Beth-el to protect Ai, it could easily have been frustrated. But no one suspected any danger, and therefore no such attempt was made. The men of Beth-el and Ai took the road that was left open to them and pursued the Israelites, probably down the ancient way past Michmash towards the Shebarim, leaving Beth-el and Ai both unprotected. After they had gone some distance, about a mile or a mile and a half from Ai, this road would bring them past the lower end of the ravine in which the ambush was posted. A second chain of outposts would easily take the signal from Joshua when this point had been passed, and then all was over with the town of Ai.

It is curious that we do not hear of the capture of Beth-el at this time, though it would have been perfectly easy to take it. The king of Beth-el is named in the list of those whom Joshua smote (Joshua 12:16). We read of its capture in Judges 1:22, and of the “entrance into the city” being sought for and betrayed. But that can hardly have been the first capture of the town.