Matthew Poole and continuators on 1 Kings 15:6

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

Which was said, chap. 14. 30. and may be here repeated to signify the Cause and Original of the War between Abijam and Ieroboam, which is implied here, and particularly described, 2 Chron. 13. Abijam continued the War which Rehoboam had begun, and pushed it on to a decisive Battel. But the place may be thus rendred, Yet there was war, &c. i. e. Although God was pleased to shew so much respect to David, as for his sake to continue the Succession to the Kingdom in his Posterity, yet he thought fit to manifest his displeasure against David's Successors for their sins, and to mix their honour and happiness with Wars and Troubles.