Charles Ellicott Commentary 1 Kings 15:16

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

There was war ... — According to 1 Kings 15:33, Baasha reigned from the third to the twenty-seventh year of Asa. The phrase, here repeated from 1 Kings 14:30, 1 Kings 15:7, appears simply to mean that the old hostile relations remained, combined with, perhaps, some border war; for it is expressly said in 2 Chronicles 14:1, that Asa’s first ten years were peaceful, and the open war with Israel did not break out until after the victory over Zerah, in his fifteenth year.