Joshua spent that night with the people

Joshua 8:1-35
Joshua spent that night with the people before they attack Ai. To encourage Israelite.
Not a man remained in Ai or Bethel who did not go after Israel. They left the city open and went in pursuit of Israel.
But Israel did carry off for themselves the livestock and plunder of this city, as the Lord had instructed Joshua.
Then Joshua built on Mount Ebal an altar to the Lord, the God of Israel, as Moses the servant of the Lord had commanded the Israelite. He built it according to what is written in the Book of the Law of Moses—an altar of uncut stones, on which no iron tool had been used. 
Afterward, Joshua read all the words of the law—the blessings and the curses—just as it is written in the Book of the Law.
Why?
The evidence of the mount at Et-Tell is difficult to accord with the biblical record here - which suggests that this may not in fact be the correct site of Ai. But see 'Cities of the conquest'. Joshua's flight and ambush strategy makes capital out of Israel's previous defeat.
From Ai, Joshua moves 32 km north to establish himself at Shechem, in the valley between Mts Ebal and Gerizim. In God's name he takes possession of the land. And the covenant is sworn as Moses had commanded.
Stay with people may encourage his people, we are family.
How?
Joshua listen to the Lord and encourage his people, so he is very good leader of Israel.