In May 1419, Joseon dispatched approximately 17,000 troops to Tsushima Island in response to an invasion by Japanese pirates. This operation, known as the Gihae Eastern Expedition, involved battles over a span of ten days before the Joseon forces returned. At that time, Japanese pirates were active along the Hwanghae Province after advancing through Jeolla and Chungcheong Provinces. Recognizing that their ultimate target was China, Taejong initiated the expedition. The pirates continued northward, utilizing island waterways in Pyeongan Province and Liaodong as they approached Liaodong. Ming forces, alerted by beacon signals from Wangjiasan Island (modern Guanglu Island), defeated the advancing pirates. Later, in the 17th century, envoys from Joseon used the sea route between Pyeongan Province and Guanglu Island to reach China, highlighting the close maritime link between these regions.
The scope of Japanese pirate raids on the Korean Peninsula and China expanded to the northern coastal areas after 1350 years. Events from 1419 suggest that Japanese pirates targeting Shandong and Liaodong may have used the islands in the northern Yellow Sea between Korea and China as a route. Comparisons of records from 1358 to 1418 reveal that incursions into China’s Shandong and Liaodong regions often coincided with attacks on the northern coastal areas of the Korean Peninsula. Diplomatic records between Korea and China also indicate instances where pirates who raided China’s northern Yellow Sea regions had previously passed through the Korean Peninsula. This suggests that the pattern of raids observed in 1419 had been established since 1350 years.
Following the Gihae Eastern Expedition, there were occasional small-scale pirate incursions into southern Korean (Hasamdo) and southeastern Chinese coastal regions. However, between 1419 and 1523, the northern Yellow Sea saw only two recorded incursions in Shandong, with no additional incursions north of the Yellow Sea. The appearance of pirates in Hwanghae Province in 1523 was viewed as an unexpected event by officials and residents in Liaodong, as well as by the King of Joseon, indicating that pirate incursions into the northern Yellow Sea had become almost nonexistent for nearly a century following the Gihae Eastern Expedition.
Japanese pirates, needing supplies such as food and water, relied on northern Yellow Sea coastal areas of the Korean Peninsula as intermediate bases. However, the Gihae Eastern Expedition restricted their access to Tsushima Island, the primary staging point for their incursions into Korea. With Tsushima under control, access to Korea’s northern Yellow Sea coast was effectively blocked. The Gihae Eastern Expedition thus marked a pivotal event in East Asian maritime history, concluding a prolonged period of pirate invasions into the northern Yellow Sea regions that had persisted since 1350.