Although ascending to the throne in 1213, Gojong did not wield much power until powerful advisors were killed off. In 1216, the Khitan invaded but was defeated. In August 1232, Gojong moved the capital of Goryeo from Songdo to the island of Ganghwa and started the construction of significant defenses there, in order to better defend from the Mongol threat. Gojong resisted the Mongol invasion for nearly thirty years before the kingdom was forced to surrender to the Mongols in 1259; Gojong died soon after.
In 1251, the carving of the Tripitaka Koreana, a collection of Buddhist scriptures recorded on some 81,000 wooden blocks, was completed. The work was perhaps motivated by Gojong's hopes to change fortunes through the act of religious devotion; however the originals were later destroyed by the Mongols — the existing Tripitaka is a replica of Gojong's original, and was commissioned around one hundred years after the originals were lost.