The first Mongol invasions of 1231 forced the Koreans to capitulate and reconsider their defensive posture.
In an attempt to overthrow the newly imposed tributes of the Mongols, the Koreans (at the command of Choe U) relocated their royal court and the population of Gaesong on the mainland to a more defensible location on Ganghwa Island in the Bay of Gyeonggi in 1232. Over time, this island became a fortress stronghold capital. The royal family and commanders weathered many campaigns by the Mongols. They commanded from Ganghwa Island until they were forced by the Mongols to move the capital back to the mainland in 1258.
The Koreans similarly evacuated to Ganghwa Island during the first Manchu invasion in 1627. During the second invasion, the Manchu forces ensured this would not happen by blocking off the island to prevent resistance, leading to their quick victory.
It is obvious that the invasions share similarities in that they were stymied by the strategic bastion that was Ganghwa Island.
Are there additional tactical or strategic similarities that both Mongol and Manchu invasions shared during their conquest of the Korean Peninsula?