Albert Barnes Commentary 1 Kings 15:16

"And there was war between Asa and Baasha king of Israel all their days." — 1 Kings 15:16 (ASV)

Baasha became king of Israel in the third year of Asa (1 Kings 15:33). The petty warfare that ordinarily prevailed on the borders of the two kingdoms continued “all the days” of Asa and Baasha. During the first ten years of Asa’s reign, he was little molested (2 Chronicles 14:1, 6).