'Army' in the Bible

Then they returned to Joshua and said to him, “Do not make all the people go up [to fight]; have only about two thousand or three thousand men go up and attack Ai; do not make the entire army go up there, for they [of Ai] are few.”

So they stationed the people, all the army—the main encampment that was north of the city, and their rear guard on the west side of the city—and Joshua spent that night in the valley.