Joshua 8:12

Five thousand men. See on verse 3. The following explanation has been given as to the assignment of the group. There are two ravines, which come to a head between Bethel, the modern Beitin, and Ai, et-Tell. The body of men who were to attack and fire the city were posted in the ravine nearer to Ai. When they should leave their ambush to attack the city, it would be necessary to have someone to protect their rear and ward off any men of war who might sally forth from Bethel to assist the king of Ai. The 5,000 would then be posted in the other ravine with their eyes toward the west in defense against Bethel. They were probably the ones who took care of the men of war from Bethel, so that they were not able to attack Joshua’s men in the rear. However, the mention of the troops from Bethel also pursuing the Israelites (verse 17) suggests that this ambush was likely involved in another part of the stratagem.