In 1232, Choe Woo, the then military dictator of Goryeo, against the pleas of both King Gojong and many of his senior civil officials, ordered the Royal Court and most of Gaesong's population to be moved from Songdo to Ganghwa Island in the Bay of Gyeonggi, and started the construction of significant defenses to prepare for the Mongol threat. Choe Woo exploited the Mongols' primary weakness, fear of the sea. The government commandeered every available ship and barge to transport supplies and soldiers to Ganghwa Island. The evacuation was so sudden that King Kojong himself had to sleep in a local inn on the island. The government further ordered the common people to flee the countryside and take shelter in major cities, mountain citadels, or nearby offshore islands. Ganghwa Island itself was a strong defensive fortress. Smaller fortresses were built on the mainland side of the island and a double wall was also built across the ridges of Mt. Munsusan. The Mongols protested the move and immediately launched a second attack. The Mongol army was led by a traitor from Pyongyang called Hong Bok-won and the Mongols occupied much of northern Korea. Although they reached parts of the southern peninsula as well, the Mongols failed to capture Ganghwa Island, which was only a few miles from shore, and were repelled in Gwangju. The Mongol general there, Saritai, was killed by the monk Kim Yun-hu amidst strong civilian resistance at the Battle of Cheoin near Yongin, forcing the Mongols to withdraw again.