1 Kings 14:30

And there was war [cf. 2 Chronicles 12:15 , "wars." Keil argues from the prohibition of war by Shemaiah ( 1 Kings 12:23 ) that this must mean "hostility, enmity." But מִלְחָמָה surely implies more than angry feelings or a hostile attitude; and it is highly probable that, even if there were no organized campaigns, a desultory warfare was constantly carried on on the borders of the two kingdoms. It is also possible that Jeroboam took a part in the war of Shishak] between Rehoboam and Jeroboam all their days.