Since 905, Tĩnh Hải circuit had been ruled by local Vietnamese governors like an autonomous state.^[115] Tĩnh Hải circuit had to paid tributes for Later Liang dynasty to exchange political protection.^[116] In 923, the nearby Southern Han invaded Jinghai but was repelled by Vietnamese leader Dương Đình Nghệ.^[117] In 938, the Chinese state Southern Han once again sent a fleet to subdue the Vietnamese. General Ngô Quyền (r. 938–944), Dương Đình Nghệ's son-in-law, defeated the Southern Han fleet at the Battle of Bạch Đằng (938). He then proclaimed himself King Ngô, established a monarchy government in Cổ Loa and effectively began the age of independence for Vietnam.