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 charioteers, but he escaped at night under cover of darkness. Jehoram's army, however, deserted him and fled.
References for 2 Kings 8:21
Edom has been independent from Judah to this day. The town of Libnah revolted about that same time.