Wihwado Retreat

The twenty-second day of the fifth lunar month

The date usually printed as 22 May is the twenty-second day of Goryeo's fifth lunar month, not 22 May on a European solar calendar. The National Institute of Korean History converts it to 26 June 1388, and on that day Yi Seong-gye and Jo Min-su turned the expeditionary army back across the Yalu River from Wihwa Island.

Ming's announced Tieling commandery claim had prompted King U and Choe Yeong to launch the Liaodong expedition. The official scholarly encyclopedia's reconstruction counts 50,464 personnel — 38,830 left- and right-army troops plus 11,600 attendants — and 21,682 horses.

Requests refused

Repeated requests to withdraw had been rejected by King U and Choe Yeong. The recorded complaints were hunger, deep floodwater and the difficulty of advancing during the rains.

No Ming army confronted Yi on the island. The obstacles in the record are weather, flooding, supplies, disease risk and desertion, alongside his wider strategic objections.

Yi persuaded the commanders to turn back and confront the king's advisers rather than cross into Ming territory.

Ten days to Gaegyeong

The army began marching south, but it did not attack the capital that day. It entered Gaegyeong on the third day of the following lunar month — 6 July in solar conversion — defeated the defenders and arrested Choe Yeong; King U was deposed soon afterwards.

The reversal was not Yi's act alone. Jo Min-su commanded the other half of the expedition and joined the decision, and whether it was a preplanned coup or an improvised seizure of opportunity remains debated.

The Goryeosa shows Yi on a white horse with a red bow and white-feathered arrows, waiting on the riverbank until the whole army had crossed — a chronicle compiled under the dynasty he later founded, which calls him Taejo.