Joshua 8:11-13

11All the troops who were with him went up and approached the city, arriving opposite Ai, and camped to the north of it, with a valley between them and the city.

12Now Joshua had taken about five thousand men and set them in ambush between Bethel and Ai, to the west of the city.

13The troops were stationed in this way: the main camp to the north of the city and its rear guard to the west of the city. And that night Joshua went into the valley.