דברי הימים ב, פרק כ״ה, פסוק כ״א

The rising tensions between the Kingdom of Israel and the Kingdom of Judah finally erupt into open conflict, leading to a decisive military confrontation. Joash, the King of Israel, launches a campaign against Judah, and the two opposing kings and their armies meet on the battlefield to engage in direct, organized, face-to-face combat [מצודת דוד, ביאור שטיינזלץ].

This critical clash takes place at Beth-shemesh. The specific location of the battle provides important context for the events that immediately follow. Because Beth-shemesh is situated very close to Jerusalem, it clarifies a geographic detail regarding the fate of the defeated king. When Amaziah, the King of Judah, is captured by the opposing forces, this proximity explains why he is taken directly to nearby Jerusalem, rather than being transported far away to Samaria, the capital city of the Kingdom of Israel [רש״י].