Take the whole army with you, and go up and attack Ai

 Joshua 8:1-29

Then the Lord said to Joshua, “Do not be afraid; do not be discouraged. Take the whole army with you, and go up and attack Ai. For I have delivered into your hands the king of Ai, his people, his city and his land. You shall do to Ai and its king as you did to Jericho and its king, except that you may carry off their plunder and livestock for yourselves. Set an ambush behind the city.”

Joshua and all Israel let themselves be driven back before them, and they fled toward the wilderness. 

Then the Lord said to Joshua, “Hold out toward Ai the javelin that is in your hand, for into your hand I will deliver the city.” So Joshua held out toward the city the javelin that was in his hand. As soon as he did this, the men in the ambush rose quickly from their position and rushed forward. They entered the city and captured it and quickly set it on fire.

When Israel had finished killing all the men of Ai in the fields and in the wilderness where they had chased them, and when every one of them had been put to the sword, all the Israelites returned to Ai and killed those who were in it. Twelve thousand men and women fell that day—all the people of Ai. For Joshua did not draw back the hand that held out his javelin until he had destroyed all who lived in Ai. But Israel did carry off for themselves the livestock and plunder of this city, as the Lord had instructed Joshua.

The evidence of the mound at Er-Tell is difficult to accord with the biblical record here - which suggests the this may not in fact be the correct site of Ai. Joshua's flight and ambush strategy make capital out of Israel's previous defeat.

Why?

In the war to Ai, Israelites once again worked together and Joshua follows God's command to attack Ai, God has his strategy and smart way. 

This time the Lord allowed Israelites may carry off their plunder and livestock for themselves. God knows people's desires, but the first fruit of the war belongs to the Lord.

How?

Honor the Lord first then we won't lack anything. For God is good, and God is great, what we have to do is put the Lord as the first priority in my life.