Joshua 8:9

Joshua therefore sent them forth
The thirty thousand chosen men:

and they went to lie in ambush;
as they were ordered, ( Joshua 8:2 ) :

and abode between Bethel and Ai, on the west side of Ai;
for as Ai was on the east of Bethel, ( Joshua 7:2 ) . Bethel must be on the west of Ai, as Jarchi notes:

but Joshua lodged that night among the people;
the main body of the army, to direct them in the affair of war, how they should behave the next day, when they came to fight; and to inspire them with courage and confidence, that they might not be afraid, because of their having been smitten before by this people, so Ben Gersom; or rather that he and they might be ready in the morning to march towards Ai, as Jarchi and Kimchi.