Which dynasty started using the civil service exams to hire government employees?

The Sui Dynasty (581–618 AD) in China is credited with the initial establishment of the civil service examination system, but it was during the Tang Dynasty (618–907 AD) that the system was significantly expanded and formalized. The exams were designed to select candidates for government positions based on merit rather than birthright, laying the groundwork for a bureaucratic system that would influence Chinese governance for centuries. This merit-based approach was further refined during the Song Dynasty (960–1279 AD), solidifying the importance of the civil service exams in recruiting officials.