The Goryeo Dynasty was established in 918 and at first acknowledged Tamna as an independent state. However, Tamna lost the status 180 years later in 1105 when the Goryeo government named Tamna a local administrative district, Tamna-gun. The new cultural elements of Buddhism and celadon were introduced to the island. Many temples were also built during this time. Following the war between the Goryeo Dynasty and the Mongol forces, the Sambyeolcho (a military unit that performed police and combat duties during the Goryeo period) resisted the invaders until the end from its last bastion on Jeju. However, in 1273, the Sambyeolcho was defeated by a combined Goryeo and Mongol force, and Tamna became the Tamna Commandery under the direct rule of the Mongols. The Mongols built ranches in the sprawling hilly and mountainous interior of the island where they raised free-roaming horses. In 1295, the name Tamna was changed to Jeju, meaning a town across the sea, and it has remained in use to this day.