The Ōei Invasion (応永の外寇, Ōei no gaikō), known as the Gihae Eastern Expedition (기해 동정) in Korea, was a 1419 invasion from Joseon against pirate bases on Tsushima Island, which is located in the middle of the Tsushima Strait between the Korean Peninsula and Kyushu.The Japanese identifying phrase derives from the Ōei era (1394–1428), which is the Japanese era name (nengō) of the calendar system then in use in Japan.