Abijah was the son of Rehoboam, whom he succeeded to the throne of Judah. He began his three year reign with a strenuous effort to bring back the ten tribes his father had last to Jeroboam. He led off the war with an impassionate appeal.
Don't you know that the LORD, the God of Israel, has given the kingship of Israel to David and his descendants forever by a covenant of salt? "And now you plan to resist the kingdom of the LORD , which is in the hands of David's descendants. You are indeed a vast army and have with you the golden calves that Jeroboam made to be your gods. (2 Chroncles 13:5,8)
It was a hyprocritical call because Abijah didn't worship the Lord any more than his father did.
Even as he orated, Jeroboam's army surrounded him in an ambush. A bloody battle followed. Eventually the Lord gave Abijah the victory, but only to preserve the promise made to King David. No fewer than 500,000 of the army of Israel perished on the field.