By the order of the Mongol Court, Wonjong moved the capital from Ganghwa Island to Kaesŏng. Regaining power from military officials with the support of the Mongols, the king decided to abolish the Sambyeolcho . Resentful of the peace terms worked out with the Mongols, the Sambyeolcho, led by Bae Jungson , revolted against the government. Systematically blocking passage between Gangwha and the mainland, they brought nearby islands and coastal regions under their domain. Wang On, a royal kinsman was proclaimed king of the maritime kingdom. They gave up Ganghwa Island and fled to Jindo Island in the southwest. Although the Sambyeolcho raided the coastlines of Jeolla Province, the southwestern province, Jin Island started to face food shortages in January 1271. In February the court of Kublai Khan's Yuan dynasty called for the Sambyeolcho's surrender. In response, its leader, Bae Jungson, asked Kublai Khan to secure Jeolla Province and put it under the direct rule of the empire, just as preceding rebels had. But his request was never fulfilled. In April, the Yuan court decided to crush the rebels. It only took a month until Jin Island fell to a combined Goryeo and Mongol army. The puppet king was killed and the survivors, led by Kim Tongjeong , fled to Jeju Island. The rebels captured the island and banished the king of Tamna in November 1270. The Sambyeolcho laid low until the end of 1271. During that time, they sought help from Japanese Kamakura Shogunate. They regained their strength to some degree the following year. They repeatedly looted the Korean coast. A combined Goryeo-Mongol assault began in February 1272, and crushed the rebels in April. Thereafter, the Mongols directly controlled Tamna until 1294.
Question: When did the Jin Island fall to the combined Goryeo and Mongol army?
Answer: May 1271