מלכים א, פרק י״ב, פסוק כ״א

The fracturing of the kingdom is perceived by Rehoboam as an outright rebellion against his rule, prompting him to respond swiftly with military force. Armed with a well-organized and trained army, he plans to strike immediately. His strategy is to take advantage of the fact that the other tribes of Israel have not yet had the time to properly organize, allowing him to quickly force them back under his control [ביאור שטיינזלץ].

To execute this campaign, Rehoboam mobilizes the tribes of Judah and Benjamin. The alliance between these two tribes is a natural one, stemming from their closely shared geographic borders [רש"י] as well as their long-standing friendly relations [ביאור שטיינזלץ]. Yet, Rehoboam’s camp is not limited strictly to them. Israelites from other tribes who reside in Jerusalem maintain their loyalty to him. It is also highly likely that parts of the tribe of Simeon remain under his authority, given that their ancestral lands are scattered enclaves entirely surrounded by the territory of Judah [רלב"ג].

The soldiers prepare for battle with absolute certainty in their impending success. They march out fully confident that God will secure their victory, trusting in the divine promise that the right to rule belongs permanently to the House of David [מלבי"ם]. Rehoboam puts immense effort into gathering this massive force in Jerusalem to reclaim his kingdom from Jeroboam, but the clash is ultimately avoided. God commands the prophet Shemaiah to intercept the army and deliver a clear message: the division of the kingdom was brought about by God Himself. Once the soldiers hear this divine decree, they stand down and refrain from going to war [אברבנאל].