1 Kings 15:6

And there was war between Rehoboam and Jeroboam all the days of his life.

Cross-reference

1 Kings 15:16 uses the same 'there was war' phrasing for Asa and Baasha, continuing the pattern of conflict between Judah and Israel.

2 Chronicles 13:3 Historical context

2 Chronicles 13:3 details the massive armies in the battle between Abijah and Jeroboam, a specific event from the ongoing war mentioned here.

2 Chronicles 13:2 repeats a similar war statement for Abijah versus Jeroboam, parallel to the one given here for Rehoboam.