Balhae was destroyed by the Khitan Liao dynasty in 926, and was formally annexed in 936. Over the next nine to ten centuries the region was administered by the Liao (Khitans), Jin (Jurchens), Yuan (Mongols), Ming and finally, the Qing, which was established by Manchus. Eventually, the Qing dynasty succeeded in unifying China by replacing the Ming dynasty. In 1712, the border between Qing and Joseon was formally demarcated. For years, Qing officials did not allow people to move to Northeastern China, as it believed that should a Han majority government rise again in parts of China south of the Great Wall, the Manchus could retreat to their original homeland. Joseon officials also did not allow its subjects to move to Northeastern China. These governmental regulations, with the general marshy nature of the area, left these lands north of the Tumen River relatively undeveloped and the region was sparsely populated by Manchu tribes for a long time. Qing officials regularly inspected this region and occasional Korean intruders were detained and sent back to Korea. However, by the late 19th century, peasants in northern Korea migrated to northeast China to flee famine and poverty. Even more arrived as refugees when Japan invaded Korea in 1894. From 1901, The Korean Empire prepared the invasion of Jiandao and take control of the area. In order to invade, Korean General Yi Hak-gyun, Diplomat Sands in Korea, and captain Payeur was sent to observe Jiandao. The French envoy, Victor Collin de Plancy, reported that Korean government is trying to get taxes from the people, increase their influence, and supplying jobs by sending officials there. The Russian legation was opposed the invasion because this might cause the loss of Korea's territory. Korean government tried to colonize Jiandao. In 1901, Korea deployed police force in Jiandao, which was active until 1906. The Korean Government sent Yi Beom-yun, who was not part of the Imperial Korean Army, as a Jiandao observer to invade Jiando in 1903. In Jiandao, Yi established Sa-po dae, which is militia consisted of Righteous army, and Imperial Korean Army. This army fought against Japan during the Russo-Japanese War. The Korean government claimed that there is no document that explicits Jiandao being part of the Qing territory. After the Russo-Japanese War, Japan began the process that led to the formal annexation of Korea. In 1905, the Korean Empire became a protectorate of the Imperial Japan,