1. Overview
Sō Yoshitoshi (宗 義智Sō YoshitoshiJapanese, 1568 - January 31, 1615) was a prominent Japanese daimyō who served as the 20th head of the Sō clan and the first lord of the Tsushima Fuchū Domain during the late Sengoku period and early Edo period. Based on Tsushima Island, which held a unique strategic and economic position between Japan and Joseon Korea, Yoshitoshi became a central figure in the complex diplomatic relations between the two nations.
His career was marked by significant involvement in Toyotomi Hideyoshi's invasions of Korea in the 1590s, where he led the vanguard of the Japanese forces. Despite his military role, Yoshitoshi consistently sought to avoid conflict and later worked tirelessly to restore peaceful relations and trade with Joseon. His diplomatic efforts often involved controversial deceptions, including the forging of official correspondence, which, while initially successful in achieving his goals, led to future diplomatic scandals. Yoshitoshi's actions profoundly shaped the relationship between Japan and Korea for decades, securing the Sō clan's unique intermediary role under the Tokugawa shogunate.
2. Early Life
2.1. Birth and Family
Sō Yoshitoshi was born in 永禄EirokuJapanese 11 (1568), the fourth or fifth son of Sō Masamori, the 15th head of the Sō clan. His mother was Ryūan-in, daughter of Tateishi Takahiro. Yoshitoshi's initial name was Akikage (昭景AkikageJapanese), a name bestowed upon him by Ashikaga Yoshiaki, the 15th (and last) shogun of the Muromachi shogunate, in December 1577. He later received the character "Yoshi" (吉YoshiJapanese) from Toyotomi Hideyoshi (then Hashiba Hideyoshi), changing his name to Yoshitoshi (吉智YoshitoshiJapanese, though pronounced the same as 義智). He eventually settled on the name Sō Yoshitoshi (宗 義智Sō YoshitoshiJapanese).
Yoshitoshi married Myō (妙MyōJapanese, died 1605), the daughter of Konishi Yukinaga, a prominent Christian daimyō. She was baptized with the Christian name Maria. His second wife was Itoku-in, from the Kawamura or Abiru clan. His eldest son and successor was Sō Yoshinari.
2.2. Succession to Headship
The succession to the Sō clan headship was complex due to the early deaths of his elder brothers. Yoshitoshi's elder brother, Sō Shigehisa, was adopted by the 17th clan head, Sō Yoshichō (also romanized as Sō Yoshishige), and succeeded him. However, Shigehisa died prematurely. His second elder brother, Sō Yoshizumi, then succeeded Shigehisa but also died young. Consequently, in January 天正TenshōJapanese 7 (1579), Yoshitoshi was adopted by Sō Yoshichō and became the 19th (or 20th, depending on the counting method) head of the Sō clan. Some accounts suggest his succession occurred in 1580.
In May 天正TenshōJapanese 15 (1587), as Toyotomi Hideyoshi's Kyūshū Campaign began, his adoptive father Yoshichō temporarily returned to the headship, and Yoshitoshi ceded control. Both Yoshitoshi and Yoshichō pledged allegiance to Hideyoshi, who confirmed their control over Tsushima Province. After Yoshichō's death in 天正TenshōJapanese 16 (1588), Yoshitoshi once again assumed the headship of the Sō clan, a position he would hold for the remainder of his life.
3. Diplomacy and Relations with Joseon
3.1. Hideyoshi's Demands and Negotiations
Following the unification of Japan, Toyotomi Hideyoshi harbored ambitions of conquering Ming China, a goal he inherited from his deceased lord, Oda Nobunaga. Practical reasons, such as the large number of armed forces under his command, also motivated Hideyoshi, as these forces could pose a threat to internal stability. To achieve this, Hideyoshi sought to re-establish diplomatic relations with Joseon Korea and coerce Joseon into joining his campaign against Ming China.
In April 天正TenshōJapanese 14 (1586), Hideyoshi sent a message to Sō Yoshichō, informing him of his impending Kyūshū Campaign and instructing the Sō clan to assist the Japanese forces in their future attack on Joseon. In June 1587, Yoshichō and Yoshitoshi met Hideyoshi, who confirmed the Sō clan's rule over Tsushima but demanded that they negotiate for the Joseon king to visit Kyoto. Hideyoshi warned that failure to comply would result in a military invasion of Joseon.
Yoshitoshi, alongside his father-in-law Konishi Yukinaga, was strongly opposed to war. Tsushima's economy was heavily reliant on trade with Joseon, and any conflict would severely disrupt their livelihood. Furthermore, Tsushima's strategic location meant it would become a critical staging ground for any invasion, exposing it to direct military impact. Thus, preventing war was crucial for the Sō clan's survival and prosperity.
Yoshitoshi was tasked in 1589 with delivering Hideyoshi's demand to Joseon that they either join his campaign against China or face war with Japan. However, Yoshitoshi, driven by his clan's vested interest in preventing conflict, deliberately delayed the talks for nearly two years. When Hideyoshi renewed his demands, Yoshitoshi, instead of conveying the true message, manipulated the diplomatic visit to the Joseon court into a campaign to improve relations between the two countries. He successfully secured a Joseon diplomatic mission to Japan, which arrived in November 天正TenshōJapanese 18 (1590).
The Joseon envoys, including Hwang Yun-gil and Kim Seong-il, believed they were sent to congratulate Hideyoshi on Japan's unification. However, Yoshitoshi had falsely informed Hideyoshi that the mission was a formal act of submission. When the envoys met Hideyoshi, they received a message, which had been redrafted at Yoshitoshi's request due to its initial discourteous tone, inviting Joseon to submit to Japan and join in a war against China. Yoshitoshi had further deceived both sides: he changed Hideyoshi's original demand of "conquering Ming and borrowing a path" (征明假道Seimei KadoJapanese) to "arranging a path to Ming" (假途入明Kato NyūmeiJapanese) when conveying it to Joseon. As Joseon was a tributary state and ally of Ming China, King Seonjo refused safe passage for Japanese troops. This diplomatic deception ultimately failed to achieve its goal of avoiding war and instead contributed to the eventual outbreak of hostilities.
3.2. Participation in the Imjin War
With negotiations having failed, Toyotomi Hideyoshi initiated a military invasion of Joseon, known as the Imjin War, in 1592. Due to Tsushima's strategic location between Japan and Korea, and Yoshitoshi's extensive knowledge and experience with Joseon, he was tasked with leading the first major land assault of the war.
3.2.1. Initial Offensive
Yoshitoshi was assigned to the First Division, serving as the vanguard of the Japanese forces. This division consisted of:
| Commander | Troops |
|---|---|
| Konishi Yukinaga | 11,000 |
| Sō Yoshitoshi | 5,000 |
| Matsura Shigenobu | 3,000 |
| Arima Harunobu | 2,000 |
| Ōmura Yoshiaki | 1,000 |
| Gotō Sumiharu | 700 |
| Total | 22,700 |
While Japanese sources generally list Sō Yoshitoshi's troops at 5,000, some Korean accounts suggest a figure of 1,000. Overall troop counts for the First Division also show slight variations across different historical records.
On April 12, 天正TenshōJapanese 20 (1592), Yoshitoshi, leading his 5,000 troops, departed from Ōura on the northern tip of Tsushima and landed at Busan. The following day, April 13, the Japanese launched a full-scale assault, capturing Busan. This marked the beginning of a rapid advance into Joseon territory. On April 14, they captured Dongnae, followed by Gijang and Gyeongsang Jwasuyeong on April 15. On April 16, Yangsan fell, and on April 17, Miryang. The Japanese forces continued their push, successively capturing Daegu, Indong, and Seonsan.
On April 26, Yoshitoshi's forces decisively defeated Yi Il, the Gyeongsang-do 순변사 (military inspector), at Sangju. The next day, April 27, they crossed Gyeongsang-do into Chungcheong-do. At Tangeumdae, they annihilated the Joseon army led by Sin Rip and subsequently captured Chungju. Advancing into Gyeonggi-do, they captured Yeoju on May 1. On May 2, they passed through Yongjin and reached Heunginjimun (East Gate) of Hanseong (modern-day Seoul). On May 3, the Japanese army entered the Joseon capital.
3.2.2. Engagement with Ming and Peace Negotiations
After holding a conference with other commanders in Hanseong, Yoshitoshi continued his advance northward from May 11, while his father-in-law Konishi Yukinaga headed northwest. On May 18, Yoshitoshi's forces defeated the Joseon army led by Kim Myeong-won at the Imjin River. By May 27, they had captured Kaesong, and subsequently took Seohung, Pyeongsan, Hwangju, and Junghwa in Hwanghae-do. Entering Pyeongan-do, they reached the Taedong River on June 8, where they repelled a Joseon night attack in the Battle of the Taedong River. On June 16, they occupied Pyongyang after the Joseon army abandoned the city.
On July 16, Ming Dynasty forces led by Liaodong Vice-General Zu Chengxun attacked Pyongyang, but Yoshitoshi's forces repelled them. Yoshitoshi and Konishi Yukinaga pursued the retreating Ming army, killing several Ming generals including Shi Ru, Qianzong Zhang Guozhong, and Ma Shiling. On July 29, they again repelled a Joseon army led by Yi Won-ik that attacked Pyongyang. However, the Japanese advance halted at Pyongyang due to severe supply shortages, largely caused by the successful naval blockade by the Joseon navy led by Yi Sun-sin.
In September, Ming envoy Shen Weijing initiated peace talks with Konishi Yukinaga. Yoshitoshi, along with the monk Keitetsu Genso, engaged in negotiations with Shen. On January 7, 文禄BunrokuJapanese 2 (1593), a combined force of approximately 40,000 Ming troops led by General Li Rusong and 10,000 Joseon troops led by Kim Myeong-won attacked Pyongyang. The Ming army breached the city gates, forcing the Japanese to retreat to their positions in the northern hills. Li Rusong offered safe passage if the Japanese surrendered the city, which they accepted. However, the retreat southward was arduous, as they were pursued by the Ming and Joseon forces.
The Japanese forces then concentrated in Hanseong and launched a counterattack, decisively defeating the Ming army at the Battle of Byeokjegwan. Following this defeat, the Ming army's morale was significantly dampened, and the Japanese army was also running low on provisions. This led to a renewed push for peace talks in April, though Joseon's intentions were not fully reflected in these negotiations. Shen Weijing proposed negotiations to Konishi Yukinaga and Sō Yoshitoshi in Hanseong. On May 8, Konishi, Yoshitoshi, and two Ming envoys arrived in Nagoya, meeting Hideyoshi on May 23 to discuss peace. Around this time, the Japanese forces had withdrawn to the vicinity of Busan, where they began constructing Japanese castles.
The peace negotiations ultimately failed due to Hideyoshi's exorbitant demands, which included the cession of four Joseon provinces to Japan and the marriage of a Ming princess to the Japanese Emperor. Furthermore, it was revealed that the Ming envoys who had come to Japan were not legitimate representatives of the Ming Emperor Ming Shenzong but rather imposters orchestrated by Konishi Yukinaga and Shen Weijing. In the following year, Japanese envoys, including Naitō Joan and the monk Genso, traveled to Beijing, presenting a forged national letter that omitted or altered portions offensive to the Ming court.
Shen Weijing's deceptive character and the pervasive use of deceit in these negotiations yielded no results, instead causing confusion in all involved countries. In January 慶長KeichōJapanese 1 (1596), when legitimate Ming envoys, including Li Fangting, arrived at Osaka Castle to formally invest Toyotomi Hideyoshi as the "King of Japan," the full extent of the fraudulent peace negotiations orchestrated by Konishi Yukinaga and Shen Weijing was exposed. This led to the complete collapse of the peace talks and the resumption of hostilities, known as the Jeongyu War.
3.2.3. During the Jeongyu War
In February 慶長KeichōJapanese 2 (1597), Toyotomi Hideyoshi ordered a second invasion of Joseon. The primary objective was to conquer Jeolla-do, the granary of Joseon, and to invade Chungcheong-do and Gyeonggi-do as much as possible. After achieving these goals, the plan was to construct new castles, station generals, and withdraw the remaining forces. Yoshitoshi was again part of the Left Army, operating with the same commanders as in the first invasion.
The Japanese forces advanced towards Jeolla-do, and on August 13, they commenced the Siege of Namwon. The city was captured on the fourth day. They then proceeded to occupy Jeonju, the provincial capital of Jeolla-do, thereby subjugating the entire province. The Japanese army further advanced into Chungcheong-do and Gyeonggi-do, achieving their operational objectives. As planned, they then withdrew to construct new castles on the outer perimeter of the existing Japanese castles built during the first invasion.
Yoshitoshi was stationed at Namhae Wajō as a garrison commander, while Konishi Yukinaga was at Suncheon Wajō. However, the Japanese forces faced significant challenges: key strategic points were seized by Ming forces, Joseon righteous armies rose across the country, and the Joseon navy, led by Yi Sun-sin, regained control of the seas after the Battle of Myeongnyang, effectively cutting off Japanese supply lines. This confined the Japanese forces to their fortified castles along the Yeongnam coast, centered around Busan.
On August 18, 慶長KeichōJapanese 3 (1598), Hideyoshi died at Fushimi Castle. Following his will, Tokugawa Ieyasu and the Council of Five Elders issued an order on October 15 for all Japanese troops in Joseon to withdraw. Even before the official withdrawal order, in September, Konishi Yukinaga's forces at Suncheon Wajō were under attack by Ming forces, and Katō Kiyomasa's troops at Ulsan Wajō were besieged by the combined Joseon-Ming forces.
Yoshitoshi was scheduled to rendezvous with Konishi Yukinaga at Changseon Island for their return. However, Konishi Yukinaga, along with Matsura Shigenobu, Arima Harunobu, Ōmura Yoshiaki, and Gotō Sumiharu, were trapped at Suncheon Wajō, their retreat routes blocked by the combined Joseon-Ming navy led by Yi Sun-sin and Chen Lin. Upon learning of their predicament, Sō Yoshitoshi, along with Shimazu Yoshihiro, Tachibana Muneshige, Tachibana Naotsugu, and Terazawa Hirotaka, formed a naval force to rescue them. They engaged the waiting Joseon-Ming navy in the Noryang Strait during the Battle of Noryang. During the chaos of this battle, Konishi Yukinaga and his trapped commanders successfully broke through the blockade and escaped. Yoshitoshi then returned to Japan via Busan, marking the end of the seven-year-long Korean invasions.
4. Battle of Sekigahara and Post-War Relations
4.1. Stance in the Battle of Sekigahara
In 慶長KeichōJapanese 5 (1600), Sō Yoshitoshi aligned himself with the Western Army, led by Ishida Mitsunari and Konishi Yukinaga, during the pivotal Battle of Sekigahara. He personally participated in the attack on Fushimi Castle and dispatched his retainers to the siege of Ōtsu Castle and the main battle at Sekigahara.
Despite the Western Army's defeat and the subsequent execution of many of its daimyō, including his father-in-law Konishi Yukinaga, Yoshitoshi was remarkably spared by Tokugawa Ieyasu. This leniency was primarily due to Ieyasu's urgent desire to swiftly restore diplomatic relations with Joseon, a task for which Yoshitoshi, with his unique experience and connections, was indispensable. As a condition for his survival and the preservation of his domain, Yoshitoshi was compelled by Ieyasu to sever all ties with the disgraced Konishi family. Consequently, he divorced his wife, Myō (Maria), Konishi Yukinaga's daughter, a politically motivated decision to protect the Sō clan from retribution. His territory was confirmed, and he was officially recognized as the first lord of the Tsushima Fuchu Domain.
4.2. Efforts to Resume Diplomatic Relations with Joseon
Immediately following his return to Tsushima after the war, Sō Yoshitoshi dedicated himself to the arduous task of re-establishing diplomatic relations with Joseon. His initial attempts were met with failure; envoys he dispatched, such as Kagehashi Shichidayu and Yoshizoe Sakon, were captured by Ming forces, and subsequent missions also failed to return. The fourth envoy, Ishida Jingemon, received a response from Joseon that conveyed the deep-seated resentment caused by the seven-year war and the Ming army's effective control over Joseon's military affairs.
In 慶長KeichōJapanese 6 (1601), Yoshitoshi sent Tachibana no Toshimasa to Joseon. The following year, Joseon dispatched Son Mun-uk as an envoy. In August 慶長KeichōJapanese 9 (1604), Joseon sent the monk Yu Jeong (also known as Samyeongdang) and Son Mun-uk as a "reply and prisoner repatriation envoy" (회답 겸 쇄환사Hoedap Gyeom SoehwansaKorean) to Tsushima, delivering a document that permitted Tsushima merchants to trade in Busan. In April of the following year, Yu Jeong met Ieyasu and Tokugawa Hidetada at Fushimi Castle in Kyoto. In the autumn, Yoshitoshi again sent an envoy to Busan, conveying Tokugawa Ieyasu's request for Joseon to send a formal diplomatic mission to Japan.
The Joseon court, however, set strict conditions for sending a mission: Ieyasu had to send a formal letter first, and the Japanese criminals who had desecrated the Seonjeongneung Royal Tombs near Hanseong had to be extradited. The demand for Ieyasu to send a letter first implied Japan's apology for initiating the war, and apprehending the tomb robbers was a difficult task. On November 12, Tachibana no Tomomasa from Tsushima delivered Ieyasu's letter along with two individuals, Magosaku and Madakaji, who were presented as the tomb robbers. During their interrogation, the two confessed that they had never been to Joseon or had only been to Busan, and that Tomomasa had coerced them into posing as the criminals. Despite this revelation, Joseon decided not to pursue the matter further, executed the two individuals, and agreed to send a reply and prisoner repatriation mission.
In 慶長KeichōJapanese 12 (1607), Joseon's mission, led by Yeo U-gil as chief envoy, departed Busan in late February and arrived in Fuchu on March 3. After traveling through Osaka and Kyoto, they reached Edo in late May. On June 6, they met Shogun Hidetada. On June 11, Hidetada's reply to the Joseon king was delivered to the Joseon envoys' lodging. This letter bore only Hidetada's red seal with the name "Minamoto Hidetada" (源秀忠Minamoto HidetadaJapanese) and notably lacked the title "King of Japan." In contrast, an earlier letter from Ieyasu, delivered via Tsushima, had included the "King of Japan" seal and the signature "Minamoto Ieyasu" (源家康Minamoto IeyasuJapanese), following the precedent of the Ashikaga shoguns, which treated the Japanese and Joseon monarchs as equals. It was later revealed that these seals and the Joseon king's seal on the Joseon letter had been forged by Tsushima officials.
These diplomatic exchanges culminated in the signing of the Kiyu Yakjo (己酉約条Kiyu YakujoJapanese, also known as the Keichō Treaty) in 慶長KeichōJapanese 14 (1609), which officially normalized diplomatic relations between Japan and Joseon. For his crucial role in restoring these ties, Ieyasu highly commended Yoshitoshi. The Sō clan was granted unique privileges, including the right to conduct independent trade with Joseon, effectively making them the shogunate's exclusive intermediaries for Joseon affairs throughout the Edo period (1603-1868). This position allowed the Sō clan to profit both politically and economically. Yoshitoshi himself received a special exemption from Ieyasu, requiring him to perform Sankin Kōtai (alternate attendance) only once every three years, rather than annually, although this privilege did not extend to his successors.
The Sō clan's intermediary role also ensured a continuous series of major Joseon missions to Edo (known as Joseon missions to the Tokugawa shogunate). These missions served as legitimizing propaganda for the bakufu (Tokugawa shogunate) and were a key element in Japan's emerging vision of an international order centered around Edo.
5. Tsushima Domain and Diplomacy in the Edo Period
5.1. Relations with the Shogunate and Domain Preservation
In 1603, with the establishment of the new Tokugawa shogunate by Tokugawa Ieyasu, Sō Yoshitoshi was officially granted the Tsushima Fuchū Domain with a nominal *kokudaka* of 100.00 K koku in Tsushima Province. This confirmation of his territory secured the Sō clan's position under the new regime. The Sō clan maintained this domain until the abolition of the han system in the late 19th century.
As the shogunate's designated intermediaries with the Joseon government, the Sō clan held a unique and vital role. This position not only provided them with significant political influence but also ensured substantial economic benefits through their exclusive trade rights with Joseon. The clan's ability to facilitate diplomatic missions from Joseon to Edo was crucial for the Tokugawa shogunate, as these missions served to legitimize the bakufu's authority and projected Japan's ideal vision of a regional international order with Edo at its center.
5.2. Treaty with Joseon and Diplomatic Issues
The Kiyu Yakjo of 1609, negotiated and signed under Sō Yoshitoshi's leadership, formally restored peaceful relations and trade between Japan and Joseon. However, the haste and deceptive methods employed during these negotiations would later lead to significant diplomatic controversies.
The letters exchanged between Japan and Joseon, including Ieyasu's initial letter and Hidetada's reply, were later discovered to have been forged by Tsushima officials. For instance, Ieyasu's letter bore a forged "King of Japan" seal, while Hidetada's letter was signed only with his personal name and title, omitting the royal designation. Furthermore, subsequent Joseon missions in 1617 and 1624 were also initiated based on forged letters from Tsushima.
The full extent of these forgeries came to light in 1636 during the Yanagawa Ikken (Yanagawa Incident). It was discovered that Tsushima Fuchu Domain retainers, including Yanagawa Shigenobu's son Toshinaga (智永ToshinagaJapanese), Matsuo Shichiuemon, and Shimagawa Takumi, along with a Joseon envoy named Park Dae-geun, were involved in these deceptions. As a result, Toshinaga's son, Shigeoki, was exiled to Tsugaru Province, while Shimagawa Takumi and Matsuo Shichiuemon were executed. The Yanagawa family's Buddhist temple was closed, and the graves of Yanagawa Shigenobu and Toshinaga were removed without a trace. This incident severely threatened the Sō clan's existence and highlighted the precarious nature of their diplomatic role, which relied heavily on maintaining a delicate balance through often illicit means.
6. Later Life and Death
Sō Yoshitoshi died on January 31, 1615 (the 3rd day of the 1st month of 慶長KeichōJapanese 20 in the old calendar), at the age of 48. His eldest son, Sō Yoshinari, succeeded him as the second lord of the Tsushima Fuchu Domain.
7. Faith and Personal Life
Sō Yoshitoshi was influenced by his father-in-law, Konishi Yukinaga, who was a prominent Kirishitan daimyō (Christian lord). Yoshitoshi himself converted to Catholicism and was baptized with the name "Dario." The Jesuit priest Gregorio de Céspedes, who visited the Japanese forces in Korea during the Imjin War, described Yoshitoshi as "an extremely prudent young man, learned, and of excellent character."
However, his Christian faith proved to be a political liability after the Battle of Sekigahara, when Konishi Yukinaga was executed. To distance himself and protect the Sō clan from the Tokugawa shogunate's anti-Christian policies and any association with the defeated Western Army, Yoshitoshi politically divorced his wife, Myō (Maria), Konishi Yukinaga's daughter. Following this, he is believed to have abandoned his Catholic faith.
Given Tsushima Island's unique position as an intermediary between Japan and Joseon, its lords were expected to be proficient in both Japanese and Korean. Sō Yoshitoshi was indeed fluent in the Korean language, a skill that proved invaluable in his extensive diplomatic engagements.
8. Evaluation and Controversy
8.1. Positive Evaluations
Sō Yoshitoshi's most significant achievement lies in his successful efforts to restore peaceful relations and trade between Japan and Joseon Korea after the devastating Imjin War. His negotiation of the Kiyu Yakjo in 1609 was crucial for stabilizing the region and was highly praised by Tokugawa Ieyasu, who recognized its importance for the newly established shogunate. This accomplishment secured the Sō clan's unique position as the exclusive intermediaries for Joseon affairs, granting them substantial political influence and economic benefits through their monopoly on trade. His ability to maintain the Tsushima Fuchu Domain's autonomy and prosperity despite the turbulent political landscape of the late Sengoku and early Edo periods is also considered a testament to his leadership.
8.2. Criticism and Controversy
Despite his diplomatic successes, Sō Yoshitoshi's career is marked by considerable criticism and controversy, particularly from the Joseon perspective. Joseon historical records, such as the Seonjo Sillok, often portrayed him negatively. For instance, an entry from 1603 described him and his retainer Yanagawa Shigenobu as "extremely cunning individuals" who frequently used "cajolery and threats" and engaged in "unpredictable" behavior while seeking to restore relations.
His role in the Japanese invasions of Korea, despite his personal reluctance, remains a point of contention. More significantly, his diplomatic methods were fraught with deception. He repeatedly misrepresented Hideyoshi's demands to Joseon and Joseon's intentions to Hideyoshi, including fabricating the purpose of the 1590 Joseon mission and altering the content of official letters to avoid conflict. After the war, to meet Joseon's demands for the extradition of tomb robbers, he presented innocent criminals as the culprits, knowing they were not responsible.
The most severe controversy was the discovery of the widespread forgery of official diplomatic correspondence by Tsushima officials, which culminated in the Yanagawa Ikken of 1636. While this incident occurred after Yoshitoshi's death, it was a direct consequence of the deceptive precedents he set during his negotiations. The scandal nearly led to the downfall of the Sō clan, highlighting the long-term instability caused by his expedient but dishonest diplomatic practices. His political pragmatism, such as divorcing his Christian wife and abandoning his faith to secure his clan's position after Sekigahara, also reflects a controversial willingness to prioritize expediency over personal conviction.
9. Impact
Sō Yoshitoshi's leadership and diplomatic activities had a profound and lasting impact on the Tsushima region, Japanese foreign policy, and the broader historical relationship between Japan and Korea. His successful negotiation of the Kiyu Yakjo in 1609 laid the foundation for over two centuries of peaceful relations between the Tokugawa shogunate and Joseon Korea, albeit under terms that favored Japan and were often maintained through the Sō clan's deceptive practices.
The Sō clan's unique role as the sole intermediaries for Japan-Joseon relations throughout the Edo period was a direct legacy of Yoshitoshi's efforts. This intermediary status granted Tsushima significant political and economic autonomy, allowing the domain to prosper through exclusive trade rights. The regular Joseon missions to Edo, facilitated by the Sō clan, became a crucial element of the shogunate's foreign policy, serving as a powerful symbol of its legitimacy and its perceived central role in an East Asian international order.
However, the controversies surrounding his diplomatic deceptions, particularly the Yanagawa Ikken, left a complicated legacy. While these tactics initially helped restore relations and secure the Sō clan's position, they also demonstrated the fragile and often dishonest underpinnings of the diplomatic framework he established. This legacy of manipulation contributed to a deep-seated distrust from the Joseon side, which viewed the Sō clan as "cunning" and self-serving. Ultimately, Yoshitoshi's actions ensured the survival and unique status of his domain, but they also cast a long shadow over the integrity of Japan-Korea relations during his era.