2 Chronicles 13:1

Now in the eighteenth year of king Jeroboam began Abijah to reign over Judah.

The verse dates the beginning of Abijah's reign over Judah to the eighteenth year of Jeroboam's reign over Israel. It places his reign in the period after Solomon's death and the division of the kingdom, when Jeroboam ruled Israel after the ten tribes broke away. Abijah succeeded his father Rehoboam on Judah's throne and reigned for three years.

The surrounding passage covers the period spanning Rehoboam's reign and part of Abijah's reign, with Chronicles giving a fuller account of Abijah's reign. The section in 2 Chronicles 13:1-20 records Jeroboam's reign in Israel during the reigns of Rehoboam and part of Abijah's reign. It introduces a war between Israel and Judah in which Judah was victorious and conquered.

During his reign Abijah fought Jeroboam when Judah's army was outnumbered two to one and attacked from front and rear, but after Abijah called on the Lord, the Lord helped Judah and Judah defeated Israel. As Jeroboam later tried to bring Judah under his rule, the relation of the two kingdoms illustrates that of the North and South during the American Civil War. Jeroboam's ten tribes had broken away, and Jeroboam later tried to bring Judah under his rule, as Jefferson Davis was said to be trying to establish his government over the North.