Sacrificing your children to prove what a crazy mofo you are and scare off your enemies. The bible, ya'll!
Jeroham becomes king of Israel. He's bad, but not in the Baal-worshiping sense, he worships that second set of golden calves that Jeroboam made. The king of Moab sends him 100 000 lambs, 100 000 sheep, and some wool. Then he rebels.
Jeroham goes to Jehosephat, king of Judah, and asks him to support him against the Moabites. Jehosephat agrees. They raise an army and march seven days towards the Moabites. Along the way, they run out of water. Jeroham is ready to give up and go home, but Jehosephat remembers Elisha and sends for him. Elisha tells Jeroham to fuck off and ask the gods his parents worshipped. He also says god did this to deliver them into the hands of the Moabites. However, because he has some respect for Jehosephat, he agrees to help them and asks for a minstrel. Apparently prophesying goes better with music.
Once he has some accompaniment, Elisha tells them to dig some ditches and in the morning they'll be filled with water. Then they'll be able to beat the Moabites. He instructs them to go all General Sherman on them and burn down everything, including the trees, which lots of people point out is forbidden in Deuteronomy. Big book, lots of verses, who can be expected to keep track of every single one? Only people who really, really care about denying gay rights. Not tree-huggers.
In the morning, as predicted, there is water in the ditches (miraculous dew!). The Moabites see it at sunrise and it's red, so they assume the Israelites slaughtered each other and go to grab the spoils. The Israelites pick them off like fish in a barrel, then tear down their city walls, cover the fields with stones, block the wells, hack down the trees and generally wage total war. The Moabite king tries to escape into Edom, but can't. In desperation, he sacrifices his oldest son, which convinces the Israelites that they are dealing with a proto-Kaiser Soze and gets them to leave. Hm...