Tsushima

• Japanese: 対馬 (Tsushima)

Tsushima is an island in the Korea Straits (aka the Tsushima Straits), roughly 33 miles from Busan, Korea, and 56 miles from Kyushu. The island has been, at least peripherally, incorporated into the Japanese state since ancient times, as Tsushima province, and was one of the "eight islands" referred to when the Japanese archipelago was referred to as Yashima or Ôyashima. The island was also claimed, however, by Joseon Dynasty Korea (1392-1897) and at times by modern Korean governments to have been Korean territory since ancient times. The island was generally administered as part of Kyushu (e.g. coming under the purview of the Chinzei bugyô in premodern times), and is today part of Nagasaki prefecture.

The construction of Kaneta fortress on the island in 667, built explicitly against the potential threat of Tang-Silla invasion, indicates that Japanese (Yamato state) agents extended control to the island at least that early.

Due to its prime position along maritime routes, and its peripheral location in both Korean and Japanese states, Tsushima was both a major intermediary point for regional trade, and was on numerous occasions the victim of foreign attacks, including in the 7th, 13th, 14th, 15th, and 19th centuries. Both Mongol invasions (in 1274 & 1281) visited violence upon the island before moving on to Kyushu. In the 13th-16th centuries, the island was also a major center of pirate activity. Joseon sent a naval fleet to attack pirate bases on Tsushima in 1419, in what is known as the Ôei Invasion; in 1443, the Sô and the Joseon court then reached an agreement by which the Sô would act to curb pirate activity, and to ensure that all merchants traveling to Korea were properly licensed (i.e. were not pirates, brigands, or smugglers), in exchange for stipends and trading rights from the Joseon court. In 1861, the island became the site of diplomatic incident once again, as the Russian ship Posadnik dropped anchor and demanded to build a Russian base on the island, remaining for quite a few months and refusing requests by Sô, Tokugawa, and even British authorities to leave, until ultimately word came from the Russian consul in Japan, and from Russian naval command, and the ship finally departed.

The Sô samurai clan, governors of the island since XXXX, were claimed as vassals by the kings of Joseon, as well as by the Tokugawa shogunate. During much of the medieval era, the Sô served as the chief intermediaries in Korean-Japanese diplomatic and trade relations, and under the Tokugawa, this position became even more formalized. At times in the 16th-17th centuries, the Sô also forged diplomatic documents, pretending to merely pass along communications from the shogunate, in order to either determine policy themselves, or to accrue the benefits of trade to themselves or their allies. While the Sô certainly negotiated for power against both the Joseon and Tokugawa courts, however, relations went smoothly for the most part in the 17th-19th centuries.

The removal of the Sô as domainal lords, and as Korean vassals, and the concordant further formalization of the incorporation of Tsushima into the territory of the Japanese nation-state in 1869-1871, caused considerable diplomatic tensions between Korea and Japan. The disputed status of Tsushima was resolved by the 1876 Treaty of Ganghwa, in which Joseon formally recognized the island as Japanese territory.

In 1904-1905, Tsushima then became the site of conflict once again, as many of the battles of the Russo-Japanese War, the battle of Tsushima in particular, were fought in the Straits, and as many Japanese troops were transported across the Straits to fight in Korea.