Sanpo War (三浦の乱)

The Sanpo War was a rebellion occurred in Gyeongsang Province, Korea, in 1510, provoked by the So clan, who was the shugo (military governor) of Tsushima Province, and kokyowa (Japanese residents who settled down in Korea with keeping Japanese nationality). The Korean name of this war is written as 庚午三浦倭乱 in Chinese characters (pronounced as Kogo Sanpo no Waran in Japanese), which basically means the "Sanpo Japanese Rebellion in the Kogo period."


In the fifteenth century, there existed a Japanese settlement called Sanpo in the southern part of the Korean Peninsula, and major forces in the western part of Japan such as the So clan maintained amicable relations with the Korean Dynasty using Sanpo as their base. Since maintaining such amicable relations was a heavy burden for the Korean Dynasty, they gradually increased restrictions. However, such restrictions were unacceptable to the So clan, which gave rise to a feud between the two sides (See the section on the trade restriction). An increased number of kokyowa (Japanese people living on the Korean Peninsula who had no intention of becoming naturalized Koreans) living in Sanpo also caused various problems, and the Korean Dynasties started to take a harsh stance towards them (see the "Increase in Number of Kokyowa" section). Under those circumstances, the dissatisfaction had gradually accumulated among the Japanese residents, and eventually the Sanpo War occurred in 1510 as a result of the outburst of their dissatisfaction, but this was suppressed by the Korean Dynasty (see the section of Evolution of the war). Consequently, the settlement in Sanpo was closed and the trade was largely restricted, which made the So clan have to seek other possibilities such as the dispatch of gishi (envoys under false names who were sent to Korea in order to evade trading restrictions imposed by Korea) and the concentration of trading rights in Tsushima in order to survive (see the section of the Aftermath of the war).

Background of the war

During the Middle Age, influential maritime forces called zenki-wako (early Japanese pirates) threatened East Asia, and the Korean Dynasty was obliged to take various countermeasures including the dispatch of troops, attempts to conciliate the pirates, and requests for suppression of the pirates sent to the Muromachi bakufu (Japanese feudal government headed by a shogun). The Korean Dynasty maintained the government policy that the agriculture should be the base of the country's economy, and they basically had no need to trade with foreign countries except for some materials which were not produced within the country. However, they attempted to bring the wako pirates under their control and also secured the cooperation from the forces in the western part of Japan in exchange for amicable relations; additionally, they even converted the wako pirates themselves into peace coordinators. Since Tsushima was considered one of the most important bases of the wako pirates, the So clan, who was the governor of Tsushima Province, was requested to cooperate with the Korean Dynasty, so the So clan responded to that request and eventually began to undertake active participation in the trade between Japan and Korea. When the Korean Dynasty was founded, there was no restriction on entrance ports, and foreigners who visited Korea for trade were allowed to enter any port. However, since the Korean Dynasty was afraid that the information about their defensive preparation along the territory might be leaked to the wako pirates, they limited the entry of koriwasen (ships used to deliver daily necessities such as rice, fish and salt) in 1407, so that these ships were allowed to use only the Pusanpo (port of Busan) and the Seiho (port of Sei, and this port was also called Naijiho), which both were located in Jinhae City, South Gyeongsang Province. The Dynasty also applied the same policy to shisosen (ships used to dispatch envoys) in 1410. In 1426, when a local magnate in Tsushima called the Soda clan requested free trade everywhere in Gyeongsang Province, the Dynasty rejected their request but in return they granted the clan additional permission of entry to the Enbo, a port located in Ulsan Metropolitan City. These ports, namely, Pusanpo, Seiho and Enbo, were known generically as Sanpo (literally, "three bays").

Trade restrictions

The medieval trade between Japan and Korea consisted of three trading styles: shinjo (courtesy visits with gifts) by trading envoys and kaishi (luxurious return gifts), the public trade by the Korean Dynasty, and private trade by Japanese and Korean merchants. For the Korean Dynasty, the public trade was not a source of benefits, and it was rather a great strain on the national treasury. Korea had to pay for the living expenses of traders during their stay in Korea and the transportation expenses of commodities, and these financial burdens were too heavy to be ignored. Since the number of trade transactions increased because of the development of the Japanese economy, the Korean Dynasty was no longer able to manage such financial burdens, and they finally began to restrict the trading activities. On the other side, Tsushima was a mountainous country with small arable land, so it was difficult to govern the territory only with taxes imposed on the land. Therefore, the So clan established their dominance over the territory by obtaining the revenue arose from the trade with Korea in order to have a command of influential families and place local samurai under the clan's order (this is called the Territory of the So clan). In addition, they lost their territory in the northern Kyushu because the influence of their master the Shoni clan became weak, so they had to grant their vassals the rights and interests of the trade instead of the land. Therefore they were eager for the expansion of the trade, and they could never accept the restrictions on the trade. Consequently, the So clan intended to enhance the trade using various measures, but the clan's intent triggered a conflict with the Korean Dynasty.

In accordance with the Kakitsu Treaty concluded in 1443, the Korean Dynasty decided to set the maximum number of saikensen (annual shisosen) from Tsushima at 50 per year. In response, the So clan proposed not to count tokusosen (ships used to send envoys for urgent matters) among saikansen, and requested that another policy should be applied to saikensen registered under the names of their branch families, separately from the treaty for the toshu saikensen (ships of the So head house used to dispatch envoys to Korea). The So clan also requested the Korean Dynasty to increase the maximum number of the toshu saikensen, but this request was rejected by the Korean Dynasty. Moreover, the So clan tried to increase the number of trade transactions by making up false envoys using names of clans who existed outside Tsushima or names of fictitious clans. In the trade between Japan and Korea of those days, Japan exported pepper, tanboku (sacred tree), shubeni (scarlet pigment), copper, and gold, while Korea exported cotton cloth. The Korean Dynasty raised the exchange rate of cotton cloth in 1488, because they were afraid that the state-reserved cotton cloth might run out. In 1494 they prohibited the public trade of gold and shubeni and in 1498 they prohibited the public trade of copper. Against this movement, the So clan tried to export copper by shipping it over by tokusosen which had been used only for diplomatic negotiations until then. The envoy of the So clan who visited Korea in 1500 brought 115 thousand kins (69,000kg) of copper, but the Korean Dynasty purchased only one third of the total amount and told the envoy to take the rest back to Japan. Two years later, the envoy visited Korea again and pressed the Korean Dynasty for the purchase of the remaining copper, but the Dynasty proposed they would purchase one third of the remaining copper after raising the exchange rate of cotton cloth against copper, and eventually, the negotiation ended in failure. Two years later after that, they had another negotiation, but it did not go well. In 1508, they again had a similar negotiation, although its result is unknown because any related documents are not left. This large amount of copper was not mined by the So clan, and it is thought that a large amount of copper had been accumulated as excess stock in Tsushima and Hakata due to the trade restrictions imposed by the Korean Dynasty. Dissatisfaction was growing at the So clan due to a number of conflicts over the trade restrictions, and that became one of the triggers for the Sanpo War.

Increase of kokyowa

At the outset, the Korean Dynasty considered Sanpo as just entrance ports and they did not anticipate that Japanese people would settle down there. However, since Tsushima had such poor land that it could not absorb the surplus population within the territory, some Japanese people as well as people involved in trading began to settle in Sanpo, and these people were called kokyowa. They expanded their residential area beyond the boundary of the permitted Japanese settlement, and they had various activities such as the purchase of farming land to grow agricultural products, the fishing at the coastal area of the Korean Peninsular, and illegal trading. Since the Korean Dynasty was afraid that kokyowa might become wako, they hesitated to use their administrative powers such as the police authority, the legal jurisdiction, and the authority of tax collection, and they just left the government of that area to some influential Japanese people. The Korean Dynasty was worried about the increased number of kokyowa, and they repeatedly demanded that the So clan should take measures to repatriate kokyowa. At the beginning, since the So clan did not have a command of kokyowa, they actively sent kokyowa back to Tsushima, which was the place under the control of the clan. However, after the residents who were not under the control of the So clan were cleaned up from Sanpo by the repatriation of 1436, the Sanpo Daikan (local governor in Sanpo) dispatched by the So clan began to govern this area. Consequently, the So clan became less interested in the repatriation of the residents, and the population in Sanpo increased drastically: the population was 206 in 1436, and it increased to over 1,650 in 1466, and then it eventually reached 3,105 in 1494.

The increased population of kokyowa caused various problems such as the occupation of fishing grounds by kokyowa, the pirate-like behavior by kokyowa, the consistent illegal trading accompanied by a collusive relationship between kokyowa and Koreans, tax evasion by some Korean who lived in the vicinity of Sanpo, and the emergence of Korean pirates. The Korean Dynasty described the situation of Sanpo and said, 'Sanpo is, so to speak, a tumor in the belly, and is about to collapse,' and a sence of crisis grew among them.

At the end of the fifteenth century, since the Korean Dynasty became tired of the situation, they changed their policy and started to take a harder stance towards kokyowa. The Dynasty tried to exercise their administrative powers such as the police authority, the legal jurisdiction, and the authority of tax collection that they had not been able to exercise against kokyowa until then, and the Dynasty told hensho (commanders who guard the border of the territory) to remind the residents of their obligation of tax payment, and furthermore, they arrested and executed those who had piracy activities with the support from the local governor in Sanpo. The Dynasty also appointed a higher official of the central government to be the hensho of Sanpo in order to strengthen their control. Under this situation, several incidents occurred as a result of strict control of the hensho over kokyowa, and the dissatisfaction of kokyowa finally exploded. The incidents which triggered this outburst of anger were, for example, the incident that the hensho insisted that some pirates who might or might not be kokyowa were definitely kokyowa and displayed their heads in front of the wakan as a warning, and the incident that ordinary Japanese people were killed on a false charge of pirates.

Evolution of the war

On April 4, 1510, kokyowa and reinforcements from Tsushima whose leader was Morichika SO started the Sanpo War with a force 4,500 strong. This is considered to have been systematically carried out under the leadership of the So clan. Their objectives were to defeat Hensho who abused their powers, and to persuade the Korean Dynasties to change their repressive policy over the kokyowa, such as trade restrictions, or the execution of the right to judge criminal cases and the power to levy taxes over the kokyowa.

The Japanese Army gained the control of senshiei (branch offices of the military) at Pusanpo and Seiho, and they defeated the hensho of Pusanpo and captured the hensho of Seiho alive. Subsequently, the troops at Pusanpo and the troops at Seiho went on to Torai-son (Torai Castle) and to Komogai-son (Komogai Castle) respectively, but their attacks failed due to the Korean Army's counter attacks.

Around April 9, the Japanese Army withdrew a part of their troops to Tsushima while the remaining forces got together at Seiho, and Morichika himself attempted to have peace negotiations. However, the Korean Dynasty refused his proposal for the negotiations, and on April 19, the Korean Dynasty Army attacked Seiho and succeeded in obtaining it, so the Japanese Army had to retreat to Tsushima. At the end of June, the Japanese Army again went into Korea, but they were defeated after all.

Aftermath of the war

This incident led to the rupture of diplomatic relations between Japan and Korea. This sanction was applied not only to the So clan but also to all Jushokunin (those given an official rank by the Korean Dynasties) and Tsuko Jutoshonin (those granted the permission to practice amicable relations). However, people in Tsushima who made their living from trade and the Korean Dynasty, who was totally dependent on imports from Tsushima for pepper, tanboku and copper, were obliged to get along with each other, and in 1512 they agreed on a settlement under the Jinshin Yakujo (visitor regulations which were established by the Korean Dynasty). This allowed the both parties to restart trading, and the wakan was reopened. However, the Dynasty imposed more restricted conditions such as the restriction on the entrance ports which designated Seiho as the only port where ships were allowed to enter, a 50% reduction in the number of saikensen, the abolishment of the tokusosen system, the prohibition of the settlement of Japanese nationals, and the recertification request for Jushokunin and Jutoshonin. The Bihenshi (Korean Department of Army) was set up in order to provide against insurgencies. After that, Pusanpo was also opened again because the capacity of the port of Seiho was not large enough to deal with all transactions; however, an incident called Saryang Incident (the raid carried out by Japanese pirates on Saryang Islands) occurred in 1544, and this brought a diplomatic break between these parties again. In 1547, the trade was restarted under the Treaty of Tenbun, but the Pusanpo port was the only permitted entrance port for Japanese ships, and this led to the latter-day wakan. The loss of Sanpo and the restricted trading greatly affected the So clan.The clan had to cover their loss by sending gishi whose nominal status was an Imperial envoy and by concentrating the trading rights in Tsushima.

Dispatch of false envoys

The Jinshin Yakujo imposed trading restrictions on parties who were considered equivalent to vassals of the Korean Dynasty such as the So clan, and this treaty did not intend to restrict relations with the king of Japan (the Muromachi bakufu), who had the same rank as the Korean Dynasty. The So clan focused on this and they tried to prepare gishi who pretended to be royal envoys in order to maintain relations to Korea. They had sent gishi even before the Sanpo War, but the Sanpo War made them send gishi more frequently. The So clan dispatched false royal envoys for purpose of trading, and additionally, they sent such envoys in order to gain more advantages in important negotiations such as the peace negotiations of the Sanpo War and the Saryang Incident. As a result of this, royal envoys visited Korea 22 times between 1511 and 1581 after the Sanpo War, but only 2 visits were by real royal envoys and the other 20 visits were by gishi which were prepared by the So clan. In fact, the trading restrictions imposed by the Jinshin Yakujo became a mere scrap of paper due to the dispatch of gishi. They needed ivory checks issued by the Korean Dynasty to the Muromachi bakufu to dispatch royal envoys. Since only the Otomo and the Ouchi clans had such ivory checks, the So clan required their cooperation to dispatch false royal envoys. Therefore, the So clan made great efforts to strengthen ties with both the clans.

Concentration of the trading rights in Tsushima

Before the Sanpo War, other local powers in the Kyushu and the Chugoku regions received tosho (a bronze seal which was required for trading with Korea) and also practiced amicable relations with the Korean Dynasty, but after the Sanpo War, the trading rights placed only in the hands of the So clan, which allowed the clan to monopolize the Japan-Korea trade. However, it is also pointed out that the concentration of the trading rights in the So clan had possibly existed even before the Sanpo War. Thus some influential people who were excluded from the Japan-Korea trade began to have relations with maritime merchants of Ming, and they eventually took part in the koki wako (late wako). The koki wako pirates were active mainly in the coastal areas of Ming, but they also frequently attacked the coastal areas of the Korean Peninsula and brought many troubles to the Korean Dynasty. Unlike the cases of early wako pirates, the Korean Dynasty could not take advantage of the benefit of trading rights in order to control the late wako, and they had suffered troubles caused by the late wako without any effective countermeasures until Hideyoshi TOYOTOMI issued the Kaizoku Teishirei (act to ban the piracy) in 1588.


For the Korean Dynasty, the transportation of products was especially a heavy burden, and the "Korean Dynasty's Fact Record" described that situation and said as follows:
Products to be exported are piled up on the streets, and all residents who live along the streets which Japanese people use for the travel to the capital city, both government officials and ordinary people, have to help the transportation of the products day and night; and furthermore, even women and children also have to do that duty, and cows which sink under a heavy burden just fall down on the street.'

The "Korean Dynasty's Fact Record" mentioned the incident that the Korean Dynasty gave up the investigation of a murder which occurred between kokyowa and the fact that a daikan which was sent by the So clan had the police authority and the legal jurisdiction. It is thought that the Korean Dynasty abandoned the police authority and the legal jurisdiction over kokyowa.

The Soda clan had the authority of tax collection over kokyowa instead of the So clan in 1429. Although the Korean Dynasty also wanted to impose a business tax on kokyowa, they found it difficult to carry out that idea because the Soda clan already imposed the equivalent tax, and they eventually gave up that plan. These facts prove that the Korean Dynasty was not able to use their authority of tax collection and kokyowa were under the control of the Soda clan instead of the So clan in around 1429.

In 1477, the Korean Dynasty planned to impose denso (rice field tax) on kokyowa, but they canceled this plan because they worried about the reoccurrence of wako activities. At that time, it was pointed out there was a risk that some Koreans might cheat on their tax payment by taking advantage of the tax exemption privilege given to kokyowa, and that expectation came true afterward.

The fishing area for Japanese in the Korean coastal zone was restricted by the Fishing Ban Treaty of Kokusa-to Island, which was agreed by the So clan and the Korean Dynasty. However, some kokyowa poached fish outside the designated area, and moreover, some of such kokyowa occupied some fishing areas provided for Korean people.

Illegal trading became normalized, and collusive relationships between kokyowa and Korean people were accelerated.
The major Korean participants in the illegal trading were residents around Sanpo, local merchants, and major merchants in Hansung, and the relationship between the residents around Sanpo and kokyowa was specially described as follows:
The relationship between them is more than the relationship between brothers, and moreover, they even use the same language and share food, drink, and interests.'
The Korean Dynasty worried about a leakage of their defensive preparations to wako, and they regarded the collusive relationships as a serious problem. In addition to local officials and hensho (local governors) around Sanpo, some higher-ranked officials of the central government of the Korean Dynasty began to provide merchants some assistance and participate with them in the illegal trading.

Some Korean residents around Sanpo pretended to have sold their farming land to kokyowa, and they transferred their land's ownership to some Japanese nominally in order to cheat the payment of tax imposed on their farming land.

Inspired by wako's activities, Korean pirates who pretended to be Japanese accelerated their activities. They wore Japanese style clothes, spoke Japanese, and posed as if they were Japanese. Korean pirates had been active since the 1470s, but it was difficult to distinguish the activities of Korean pirates and the activities of wako.

The crew of the ship for an envoy of the Ijuin clan postponed their departure, and they waited for the rebellion to begin in order to participate in the war. This envoy ship was operated by the So clan in fact, and considering these facts, it is thought that the Sanpo War was intentionally provoked by the So clan.