Despite working on tight rations by January of 1637, the Joseon defenders were able to effectively counter Manchu siegeworks with sorties and even managed to blow up the powder magazine of an artillery battery that was assailing the East Gate of the fortress, killing its commander and many soldiers. Some walls crumbled under repeated bombardment, but were repaired overnight. Despite their successes, Dorgon occupied Ganghwa Island on 27 January, and captured the second son and consorts of King Injo. He surrendered the day after.