II Samuel - Chapter 10
A Hasty Act Leads to War
Nachash, king of Ammon, died and was succeeded by his son, Chanun. (Ironically, "chanun" means "gracious" in Hebrew and Chanun was anything but!) David sent messengers to pay a "shiva call" to Chanun. (The consolation call was in gratitude for Nachash saving David's brother Elihu when the Moabites reneged on their promise of sanctuary.) Chanun, however, was suspicious of David's motivations. His advisors told him that the Jews were no doubt spies. Chanun punished the messengers by cutting off half their beards and half their robes, up to the seat of their pants. He then sent them away in this embarrassing state. (Had he been sure that they were spies he would no doubt simply have executed them. This was what he did because he merely suspected them. Keep that in mind next time you go through screening at the airport.) The messengers sent word to David, who replied that they should stay in Jericho (the city nearest Ammon) until their beards grow back, then return to Jerusalem.
The Ammonites realized that they had goofed and set the stage for war. They decided that if war was inevitable, they'd better make a pre-emptive strike. However, they didn't have much of an army, so they hired mercenaries from local city-states. David heard that Ammon was assembling an army, so he got Yoav to rally his forces. Yoav divided the Israelite forces into two, one half to be directed by him and the other by his brother Avishai. They fought on two fronts with the understanding that if either group was in danger of being defeated, the other would come to save it.
The mercenaries from Aram fled in battle and the Ammonites knew that without them, they could not succeed, so they also ran away. Yoav and his men returned to Jerusalem. The mercenaries regrouped. Hadadezer, king of Tzovah (last seen in chapter 8 and here called Hadarezer) joined with them for another attack. Again, David got word and prepared for battle. Aram was defeated and Israel captured their charioteers and horsemen, as well as killing their commander. Aram saw they were defeated and signed a pact with Israel. They would not hire themselves out to Ammon after that.