2 Chronicles 20:1 - 37
AMP - 1 AFTER THIS, the Moabites, the Ammonites, and with them the Meunites came against Jehoshaphat to battle. 2 It was told Jehoshaphat, A great multitude has come against you from beyond the [Dead] Sea, from Edom; and behold they are in Hazazon-tamar, which is En-gedi.
For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
God ordered the Israelites to destroy the heathens and their place of worship as they journeyed into the Promised land. However, the Moabites were one of the nations God told the children of Israel not to invade during their journey from Egypt to the promised land. (Deut. 2:4, 9).The Israelites therefore turned from them and did not destroy them.
The 'high places" in this reading refers to the places of worship of pagan gods used by the Moabites.