A military alliance between the Kingdom of Israel and the Kingdom of Judah is set into motion when the King of Israel requests assistance in a campaign to recover lost territory. This appeal to the King of Judah is not a random diplomatic move. The two monarchs have established strong personal bonds through marriage ties between their families [אברבנאל, מלבי״ם]. Furthermore, while the disputed region of Ramoth-gilead belongs directly to the Kingdom of Israel, it is viewed broadly as an inseparable part of the entire Land of Israel. This shared national heritage fully justifies a joint military effort to reclaim it [ביאור שטיינזלץ].
The King of Judah responds with complete and wholehearted agreement to join the war. The primary approach among commentators is that his declaration represents total participation on every level, promising that he, his citizens, and his military will act exactly alongside the King of Israel. A more detailed perspective breaks down this total commitment into three distinct layers. First, he affirms the personal and familial bond created by their recent marriage ties. Second, he emphasizes their shared national connection, recognizing that both of their nations are ultimately Israelites. Finally, he commits to a strategic military alliance, operating under the understanding that a mutual victory will ensure future support from the Kingdom of Israel should the Kingdom of Judah ever need it [מלבי״ם].
Despite this enthusiastic support, the decision to join forces raises a significant difficulty. The prophet Elijah had previously declared a severe decree of destruction upon the King of Israel. Standing alongside a person doomed to such a fate carries immense danger, particularly on a battlefield. To resolve this issue, two possibilities are suggested. It is possible that the King of Judah simply never heard about the prophet's harsh warning. Alternatively, he might have known about the prophecy but assumed the decree was canceled after the King of Israel humbled himself, fasted, and wore sackcloth. This assumption would have been entirely reasonable, as a noticeable period of peace and quiet had followed those acts of repentance [חומת אנך].