2 Chronicles 11:12
And in every several city he put shields and spears, and made them exceeding strong, having Judah and Benjamin on his side. And in every several city he put shields and spears, and made them exceeding strong, having Judah and Benjamin on his side.
Rehoboam placed shields and spears in every several city, strengthening Judah's fortified cities until the strongholds were made exceeding strong and very secure. Judah and Benjamin remained with him and continued on his side. Those military preparations were not the true source of Judah's early prosperity and did not account for it.
Judah's strength came from recognizing God as the supreme ruler and from seeking Him. That strength was increased by people who sought the Lord joining the kingdom.