During Jehoram’s reign, the Edomites revolted against Judah and crowned their own king.
So Jehoram went with all his chariots to attack the town of Zair. The Edomites surrounded him and his chariot commanders, but he went out at night and attacked them under cover of darkness. But Jehoram’s army deserted him and fled to their homes.
So Edom has been independent from Judah to this day. The town of Libnah also revolted about that same time.