Israel and Judah's War Against Moab
After the death of King Ahab of Israel, Mesha, the king of Moab, refused to pay his regular tribute to Israel. "The existence of this Moabite king is confirmed by an inscription on a pillar known as the Moabite Stone [now in the Louvre Museum in Paris]. The inscription indicates that Omri had conquered the plains of Moab north of the Arnon River and that the area remained under Israelite control throughout Ahab's reign" (Nelson Study Bible, note on verse 4).
To fight against Moab, the new king of Israel, Jehoram, formed an alliance with the king of Edom and with King Jehoshaphat of Judah (who should have learned from his earlier experience with King Ahaziah to not participate in such an alliance). Jehoshaphat insisted, however, on first consulting Elisha, whom, for the sake of Jehoshaphat, God inspired to prophesy victory. Then, due to God's miraculous intervention, the army of Israel defeated Moab, invaded their territory, destroyed their cities and ruined their lands, their trees and their springs of water. During a battle, the king of Moab offered in his anxiety his oldest son, who would have become king after him, as a burnt offering to his pagan god. When he did so, "there was a great indignation against [or upon] Israel. So they [the Israelites] departed from him [the king of Moab] and returned to their own land" (verse 27).
One scholar explains: "The Hebrew word translated 'indignation' is ketsef…[which here] denotes the psychological breakdown or trauma that affected the Israelite forces when they beheld the sign of human sacrifice atop the walls of Kir-Hareseth…. Apparently, it had happened before, elsewhere, and could be counted on as a kind of conditional reflex. It follows that Mesha's sacrifice of his son, rather than unprecedented, was in fact an integral, if seldom implemented, part of an age-old Canaanite tradition of sacral warfare…. Mesha's sacrifice of his firstborn, seen in this new light, was virtually guaranteed to save the lives of the entire population—men, women and children—of the city under siege" (Baruch Margalit, "Why King Mesha of Moab Sacrificed His Oldest Son," Biblical Archaeology Review, Nov.-Dec. 1986, p. 63). Israel, losing the heart to press the battle further, decided to depart.