In 854, the new governor of Annan, Li Zhuo, provoked hostiles and conflicts with the mountain tribes by reducing the salt trade and killing powerful chieftains, resulting in the defection of prominent local leaders to the Nanzhao Kingdom. The local chief Lý Do Độc, the Đỗ clan, the warlord Chu Đạo Cổ, as well as others, submitted or allied with Nanzhao.^[106] In 858 they sacked the capital of Annan. In the same year the Tang court responded by appointing Wang Shi as the military governor of Annan, aiming to restore order, strengthen the defense of Songping.^[107] Wang Shi was recalled to deal with the rebellion of Qiu Fu in Zhejiang in late 860. Northern Vietnam then degenerated back to chaos and turmoil. The new Chinese military governor, Li Hu, executed Đỗ Thủ Trừng, a prominent local chief, thus alienating many of the powerful local clans of Annan.^[108] The Nanzhao army was initially welcomed by the locals, and their joint force captured Songping in January 861, forced Li Hu to flee.^[109] The Tang managed to retake the region in summer 861. In spring 863 Nanzhao and rebels numbered 50,000 under generals Yang Sijin and Duan Qiuqian launched the Siege of Songping. The city fell in late January as the Chinese army withdrew north.^[110] The Protectorate of Annan was abolished.^[111]

The Tang launched a counterattack in September 864 under Gao Pian, an experienced general who had fought the Türks and the Tanguts in the north. In winter 865–866, Gao Pian recaptured Songping and northern Vietnam, and expelled Nanzhao from the region.^[112] Gao punished local people who had allied with Nanzhao, executed Chu Đạo Cổ and 30,000 local rebels.^[113] In 868 he renamed the region to "The Peaceful Sea Army" (Jinghai guan). He rebuilt the citadel Sin Songping, named it Đại La, repaired 5,000 meters of damaged city wall and reconstructed 400,000 bays for its residents.^[112] He was well respected even by the later Vietnamese.^[114]