- Japanese: 大島 友之允 (Ooshima Tomonojou)
Ôshima Tomonojô was a prominent Tsushima han retainer in the Bakumatsu and Meiji periods, who worked closely with Kido Takayoshi to press for taking steps to better defend Tsushima, and by extension the realm, from Western incursions. He is known for his arguments for the invasion of Korea in the early 1860s, both in order to protect Japan from the possibility of Korea falling into Western hands, and in order to benefit Tsushima or Japan economically; he also argued that such an invasion would liberate the Korean people from an unjust and repressive royal government.
Ôshima rose to prominence within domainal leadership after the assassination of domainal chief councilor Sasu Iori, and the resignation of Sô Yoshiyori as daimyô in favor of his son Sô Yoshiakira in 1862 dramatically altered the balance of power within the domain. Yoshiakira's mother, Jihô-in, herself the daughter of a former Môri clan daimyô of Chôshû domain, engineered an alliance between the two domains, and Ôshima came to be the leading Tsushima official in that relationship.
Speaking with prominent Chôshû official Kido Takayoshi about his concerns about Western incursions, and citing in particular the six-month-long confrontation with the Russian corvette Posadnik the previous year, Ôshima found an ally; the two would go on to become close lifelong friends. Ôshima's chief concern initially was the strengthening of coastal defenses at Tsushima, and the financial well-being of the domain; Kido supported this, but also advocated an invasion of Korea, in order to preemptively prevent Western powers from taking the peninsula and using that strategic position as a launchpad for attacking Japan, something that recent British and French actions in China had led Kido to believe they might do. Their fears about Western incursions were not unfounded; in addition to the Posadnik, hundreds of Western ships had been seen offshore at Tsushima over the course of the last several years, and though it had not happened quite yet at that point, the following year the British Royal Navy would shell and destroy much of Kagoshima, home to the Shimazu clan of Satsuma han.
In the 11th month of 1862, the Imperial Court announced a decision that an edict would be promulgated calling for the forcible expulsion of the barbarians. Kido and Ôshima anticipated that Westerners would respond to force with force, bringing further military and territorial difficulties for the realm, and in particular for Tsushima. With Kido's help, Ôshima was able the following month to present a memorial to the Court, expressing among other points that Tsushima's strategic location made it a prime target for Western incursions, that Tsushima's reliance on Korean commerce for financial and even alimentary well-being left it particularly vulnerable, and that if Tsushima were to fall into the hands of a foreign power, it would tarnish Imperial reputation or authority, and would provide that Western power far too powerful a position from which to then invade Chôshû or elsewhere in the realm. The Court's response, issued in the first month 1863, officially recognized for the first time Tsushima's strategic military importance for the defense of the realm, something Sasu Iori had been arguing since the 1840s.
The Court could not provide any financial support for the strengthening of Tsushima's defenses, however, so Ôshima and a number of other Tsushima officials accompanied Sô Yoshiakira as he traveled to Edo in 1863/1 to negotiate with rôjû Mizuno Tadakiyo and Itakura Katsukiyo for shogunate aid in such matters. While in Edo, Ôshima was introduced by Kido to Confucian scholar Yamada Hôkoku, a staunch advocate of the potential invasion of Korea. Three months later, he met with Itakura, discussing not only the matter of Tsushima's defense, but also the possibility of an invasion of Korea; Itakura agreed to send inspectors to investigate the situation in Tsushima, and the possibility of a Western takeover of Korea. Ôshima also met with Katsu Kaishû while in Edo, who was strongly supportive of enhancing Tsushima's coastal defenses, though historians remain divided as to whether Kaishû supported an invasion of Korea.
Following all of this preparation, Ôshima presented a formal memorial to the shogunate in 1863/5, advocating an investigation of the situation in Korea, and if deemed necessary conquer the kingdom before the Western powers had the chance to do so. Ôshima argued that protecting Korea from the Western powers in this way would lead to the Korean people viewing the Japanese as virtuous liberators; and if the Koreans resisted, he suggested, they would have to be subdued by force. In the memorial, Ôshima further characterized Tsushima's traditional diplomatic & trade relations with Korea as "failed," asserting Tsushima's inability to be dependent on such a relationship any longer, and emphasizing in particular the domain's inability to afford to both feed its people and mount a defense or response against a potential Western incursion. Of course, Tsushima also could not afford to fund such an expedition to Korea either, or to support itself when such an invasion inevitably led to Korea's shipments of rice and other provisions to Tsushima being severed. Believing that the shogunate would support his plan and launch this invasion, Ôshima went further, detailing other aspects of the preparations that would need to be made, including having the shogunate supply Tsushima with funds to support the people of the domain during such an event, and organizing enhancements to the coastal defenses of Chôshû and Kyûshû. In total, Ôshima requested an unprecedented 30,000 koku from the shogunate to help support all of these aspects of the endeavor. His request was backed by Itakura, Yamada, Kido, and Katsu.
After several weeks of deliberations, the shogunate actually approved most of Ôshima's requests - including the massive 30,000 koku grant, but not agreeing to lend any warships, or to commit to an invasion of Korea. They ordered Katsu Kaishû to travel to Tsushima, and if possible to Korea, to investigate the situation, but shortly afterwards ordered him to first escort Shogun Tokugawa Iemochi to Osaka (on the shogun's way to Kyoto), and to then attend to some pressing business in Nagasaki. Katsu never made it to Tsushima, and by mid-to-late 1864, the political situation in Edo had shifted dramatically; the shogunate turned against Chôshû, and Itakura, Katsu, and Kido all lost their prominence or influence within the government. Shogunate leaders came to see Ôshima's plans and petitions as connected to Chôshû's schemes to overthrow the Tokugawa, and so revoked their support, including revoking the 30,000 koku grant. Ôshima pressed forward with his plans, however, submitting a petition to inspector Mukôyama Kôson (a mid-ranking shogunate official, but one who was willing to listen) in 1864/10 reiterating much of the same points as his earlier petitions, but also emphasizing that the current Korean government was unjust and repressive, and that his invasion and reorganization of Korea-Japan relations could also lead to Japanese merchant communities operating and settling more freely in more Korean ports, as they had in the 16th century. While some have argued that he may have supported pushing for an invasion simply in order to retain the support of Itakura and Yamada, the fact that he continued to push for this when operating alone, even after their fall from power, indicates his belief in the idea.
Unlike many prominent policy commentators at the time, Ôshima sought economic strength from expanded or revised trade with other Asian partners (chiefly Korea and China), rather than advocating a shift to trade with Western partners.
Ôshima was somewhat more successful in working with the Meiji government. Immediately following the Meiji Restoration, even as the Court focused its efforts on clearing out the last pro-Tokugawa opposition, Ôshima encouraged the Court to re-negotiate relations with Korea. He had them elevate Sô Yoshiakira in rank, and employ him as chief Imperial representative in diplomatic relations with Korea.
Yoshiakira's attempt to engage with the Korean Court no longer as a vassal but now as a representative of a new Imperial government raised the ire of the Korean Court, however, and Japan-Korea relations faltered for quite some time, before finally being re-established under the framework of Western/modern-style international relations, in the 1876 Treaty of Ganghwa.
- Robert Hellyer, Defining Engagement, Harvard University Press (2009), 217-233, 240-241.