In the time of Jehoram, Edom1 rebelled against Judah and set up its own king.
References for 2 Chronicles 21:8
So Jehoram went there with his officers and all his chariots. The Edomites surrounded him and his chariot commanders, but he rose up and broke through by night.
To this day Edom has been in rebellion against Judah. Libnah2 revolted at the same time, because Jehoram had forsaken the LORD, the God of his fathers.
References for 2 Chronicles 21:10