2 Samuel 10 & 1 Chronicles 19 - 20
In all of David’s conquest, he didn’t attack the Ammonites because the king had been kind to him when he was running from Saul. One day, the king of the Ammonites died and his son ruled in his place.
David sent a group of men with a message of comfort to the new king. When the men got there, the Ammonite leaders said to their king, “These men aren’t here to show David’s concern for you. They aren’t here to show respect for your father. They’re spying on us. They’re scouting out our city to see where we’re weak.”
So the new king took the men and shaved off half of each man’s beard. He then cut off their robes, exposing the lower half of their bodies. The men went back to Israel deeply humiliated.
David heard about this great insult and sent word to his men. “Stay in Jericho until your beards grow back. Then return to us.”
The Ammonites finally realized what they had done. They had made David extremely angry. So they started building up their army. They even hired 33,000 soldiers from other countries.
David sent Joab and his army to fight against the Ammonites. When they were in place, the Ammonite army moved to a position where they were on one side of the Israelites, with the foreign soldiers on the other. Joab realized he was in between the two, with front lines on both sides. Therefore he split the army. He selected his best troops to fight with him and attack the foreign soldiers. Everyone else was to fight the Ammonites under the command of his brother.
Joab said to his brother, “Both of us will be ready to help the other if there’s a need. Be brave and fight hard. We must protect our people and the cities of God. May the Lord’s will be done.”
The battle was decisive. Joab and his elite troops hit the foreign armies so hard that they turned and ran. When the Ammonites saw this, they retreated back into their walled cities. With this, Joab took his army back to Jerusalem.
The foreign army reorganized and came back to fight again. This time, David went with his men and totally defeated them, killing over 40,000 men. Those who escaped went back to their country and never returned again. David waited until spring to finish defeating the Ammonites.