Jehoshaphat made peace with Israel's king Ahab with the marriage of his son, Jehoram, to Ahab and Jezebel's daughter, Athaliah. When Jehoshaphat went to visit Ahab, Ahab persuaded him to join military forces to attack the Syrians. Jehoshaphat agreed, but wanted to consult the Lord first. Ahab called together his 400 prophets who all encouraged Ahab to attack the Syrians. Jehoshaphat was suspicious. He asked Ahab for a prophet of the Lord. Ahab acknowledged Micaiah, “but I hate him, because he never prophesies good concerning me, but always evil.” Nonetheless, Micaiah was summoned. When Ahab asked God's prophet what he should do, Micaiah said, “'Go and prosper, and they shall be delivered into your hand!'” Ahab knew this couldn't be right. Ahab commanded Micaiah to speak the truth. Then Micaiah said, “'I saw all Israel scattered on the mountains, as sheep that have no shepherd.'” He went on to say that all of the other prophets were lying and that Ahab would lose his life in the battle. Ahab was furious, and directed his men to imprison Micaiah until he returned. In response, Micaiah said, “'If you ever return in peace, the Lord has not spoken by me.'”
Ahab convinced Jehoshaphat to go. In an attempt to thwart Micaiah's words, he disguised himself, but Jehoshaphat did not. Meanwhile, the king of Syria commanded his captains to focus only on killing Ahab. When they saw Jehoshaphat's robe, they assumed it was Ahab and surrounded him. But as Jehoshaphat shouted to the Lord for help, the Syrians saw that it was not Ahab and turned away. Despite Ahab's attempt to escape death, he was struck by a random arrow, and at sunset, he died.
When the Moabites and Ammonites threatened war, Jehoshaphat proclaimed a fast and prayer throughout all Judah. Jehoshaphat assembled the people in the temple and prayed to God. “'For we have no power against this great multitude that is coming against us; nor do we know what to do, but our eyes are upon You.'” In response, Jahaziel spoke forth the word of the Lord: “'Do not be afraid nor dismayed because of this great multitude, for the battle is not yours, but God's.” He related God's plan for the army of Judah and where to position themselves, but that they would not need to fight, only watch to see what God would do. “'Do not fear or be dismayed; tomorrow go out against them, for the Lord is with you.'”
The next day, they did according to the guidance, and Jehoshaphat sent the singers ahead of the army. When they began to sing praises to God, the Lord confused the Ammonites and Moabites and they killed each other. When Jehoshaphat's army reached the battlefield, there was not one survivor.
Ahaziah's son, King Jehoram of Israel, asked King Jehoshaphat to fight with him against the Moabites. Jehoshaphat agreed. When Jehoram began to panic, Jehoshaphat again asked for a prophet to inquire of the Lord. One of Jehoram's servants mentioned Elisha, and Jehoshaphat knew that he spoke for the true God. Elisha's initial reaction was contempt for Jehoram. “'What have I to do with you? Go to the prophets of your father and the prophets of your mother.'” But for Jehoshaphat's sake, Elisha received the Lord's guidance. They were to dig the valley full of ditches, and God would fill the ditches with water. Elisha said that they would be victorious and that they were to attack Moabite cities, cut down their trees, destroy their wells and fill their fields with rocks. They did as instructed and the next morning there was a flash flood.
The Moabites, looking out over the water-filled fields in the morning sun thought it was covered in blood. They thought that the armies had all killed each other, and decided to go out and collect anything of value. But they ran unarmed into Israel's camp, and Israel attacked the Moabites. Following Elisha's revelation, they pursued the Moabites and were successful.
Jehoshaphat's reign lasted 25 years. The Lord was with Jehoshaphat because his heart took delight in the ways of the Lord. He continually sought the Lord and His commandments, and kept himself from participating in Baal worship and the many idolatrous ways of Israel. (1 Kings 15:24; 22:2-50; 2 Kings 3:7-27; 2 Chronicles 17:1-21:1)