In the 9th century, the Unified Silla established a garrison on the island to combat piracy. Their commander, Wang Geon, established his military reputation at the garrison, and later went on to found the Kingdom of Goryeo. In the 13th century, the court of Goryeo took refuge on the island as Mongol forces invaded in 1232. After Goryeo capitulated to the Mongols, the elite forces on the island rose up, beginning the Sambyeolcho Rebellion.