Hideyoshi's administrative organization was remarkable. He created five bugyō; namely, a mayor of the city of Kyōto, a manager of taxation, a judicial administrator, a supervisor of the public works, and a supreme judge of civil suits. He also selected Tokugawa Iyeyasu, Uyesugi Kagekatsu, Mōri Terumoto, Ukita Hideiye, and Mayeda Toshiiye to form a council of state, called the gotairō, five elders, for the purpose of deliberating upon all weighty national affairs. The question of the land also received careful attention at his hands. Perceiving that, owing to faulty administration of the regulations, many irregularities had arisen, and estates were in many cases wrongly registered, he dispatched inspectors to all the provinces and caused accurate surveys and returns to be made, severe punishment being meted out to any officials convicted of receiving bribes in the execution of this office. The result was that large tracts of land hitherto improperly exempted from taxation were brought within the fiscal system. A radical change was also introduced in the manner of registering lands: hitherto they had been classed according to the monetary income obtained from them; thenceforth they were estimated according to their produce in kind, and the taxes were calculated on the basis of this new valuation. Speaking roughly, about two-thirds of the produce went to the state, the remainder to the cultivators of the land. Further, in view of the defective condition of the currency, Hideyoshi caused gold coins of two dimensions—ōban and koban—to be struck, as well as ingots of silver, and coins of silver and copper known as the tenshō tsūhō-sen.
In Hideyoshi's time Christianity had already obtained considerable vogue throughout the country. Oda Nobunaga had sanctioned the preaching of the foreign creed, and had built for it a place of worship, called Namban-ji, in Kyōto. But when Hideyoshi, in the course of his campaign against Shimadsu, reached Hakata, the Christian priests showed such an arrogant demeanor that Hideyoshi, enraged by their conduct, ordered that they should leave Japan by a certain day, and prohibited the people from embracing Christianity. He even went to the length of causing Namban-ji to be destroyed. Some of the converts, however, managed to conceal themselves and carry on their worship in secret. When the Tokugawa shōguns came into possession of the administrative power, the edicts against the foreign faith were strictly enforced, and steps were taken to restore to Buddhism those who had embraced Christianity. These measures were unsuccessful, however, and culminated in the Shimabara disturbances in 1637, which will be subsequently described.
We shall now relate the story of Hideyoshi's Korean expedition. It will be remembered how, during the period of the lax administration of the Ashikaga, the laws were ill respected, disorders were constant, and the littoral population took advantage of the situation to engage in piratical raids against China. These proceedings led to a cessation of intercourse between Japan and China, and Korea also, having been conquered by China, ceased to maintain friendly relations with Japan. At the same time, on Japan's part, much cause of complaint existed against Korea. The Koreans had always assisted the Yuan dynasty of Mongols in their attacks upon Japan, and had shown themselves her bitter enemies. But owing to the unceasing prevalence of internal disturbances in Japan, it was not possible to avenge the hostile acts of China and Korea. So soon, however, as domestic broils were brought to an end and the control of the administration rendered effective throughout the empire, Hideyoshi formed the project of leading an expedition against the Ming sovereigns. He had entertained this idea for some time, and had made it known to Oda Nobunaga when preparations were in progress for the campaign against the Mōri family. In 1587, after his successful expedition against the Shimadsu in Kiushū, Hideyoshi sent a dispatch to Sō Yoshitomo, warden of Tsushima Island, directing him to take steps for inviting the king of Korea to come to Japan in order to have audience of the Japanese emperor. This invitation was to be accompanied by an intimation that unless the king obeyed the summons, the Japanese forces would at once be directed against Korea. Following up this measure, he determined—in 1590, by which time the country's domestic troubles had been entirely settled—to insist on presents being sent to Japan by both China and Korea, on pain of being invaded unless they consented to take that step. He dispatched an envoy to Korea with instructions to make known his purpose, and to require that the Koreans should act as intermediaries to procure China's consent. In the event of the Koreans' refusing, they were threatened with the punishment of being compelled to march in the van of the Japanese army to the invasion of China. The Koreans, however, declined to accept such a proposition. Hideyoshi thereupon gave up the office of kwanpaku to his adopted son, Hidetsugu, and assuming the title of taikō, he decided to lead an expedition against Korea. The emperor having given his approval of the step, orders were issued to all the provinces to furnish troops and military supplies, as well as to build a great fleet of war-vessels. In 1592 Hideyoshi appointed Ukita Hideiye commander-in-chief of the army, with Masuda Nagamori, Ishida Mitsunari, and Otani Yoshitaka for his staff. The whole force, numbering, it is said, 130,000 men, was divided into eight corps, and with the van were Konishi Yukinaga and Katō Kiyomasa. The sailors of the fleet aggregated 9000, and were under the command of Kuki Yoshitaka.
In March, Hideyoshi left Kyōto, and proceeding westward worshiped at the sepulchers of the Emperor Chūai and the Empress Jingō, passing thence to Nagoya in Hizen, where the forces from all the provinces were being mustered. In April the expedition sailed from the coast of Japan. The number of ships was so great that they seemed to cover the sea and struck the Koreans with consternation. Konishi Yukinaga and his division were the first to reach Korea. They effected a landing at Fusan, and took prisoner the Korean general who attempted to defend the port.
From this point Yukinaga marched confidently on Tokunegi, overbearing all resistance and putting the enemy's officers to the sword. Shortly afterward Kiyomasa and his corps also reached Fusan, and heading for Kegushagushu, attacked and took it. Korea's opposition was soon crushed, and the whole country submitted to the vast force of invaders. Meanwhile, the king, Lien, who had not failed to convey to China intimation of the pending danger, sent to the court of the Ming sovereigns earnest appeals for succor; and his troops having been everywhere defeated by the Japanese, he finally fled from the capital with his son, and took refuge in Hegushagu, having left one of his generals to defend Kanko. The Japanese troops, everywhere victorious, pushed on to the capital, which was taken by Konishi Yukinaga, the other generals subsequently assembling there. Yukinaga now made preparations to invade Hei-ando, and Kiyomasa took Hamukyando as the scene of his next campaign. Meanwhile, Hideyoshi, forseeing that a Chinese army would be sent to aid the Koreans, dispatched reinforcements to the invading troops, and conveyed to the commanders messages of encouragement and exhortation. He was persuaded that the Japanese army would defeat the Chinese, and he believed that in the space of two years the conquest of China might be effected, in which event he purposed transferring the capital of Japan to China. He even went so far as to determine the routine to be followed in the removal of the Japanese court to China. Kiyomasa now marched northward to Hamukyando, where he took a town called Eikyo. Learning there that two Korean princes were at Kaineifu, he attacked it and took them both prisoners. Continuing his advance, he crossed the northern frontier and entered Orankai, where he destroyed the castle, taking and putting to death a number of Koreans. The impetuosity of his movements and the unvarying success of his arms filled the Koreans with dismay. They gave him the name of "Kishokwan" (i. e., the demon general), and fled at the mere news of his approach.
Yukinaga, in the meanwhile, having conquered Hei-an, the king of Korea retired from Hegushagu and would have entered Hamukyan, but finding that Kiyomasa had already overrun that district, he turned westward to Gishu (Wiju). Yukinaga marched against Kuimeigen and took Hegushagu, the Japanese troops being everywhere victorious. Things did not fare equally well with the navy, however. The ships sustained several defeats, and their intention of proceeding from Terura-do to Kanai-do to effect a junction with the army was frustrated by the Korean commander Li Shunshin, who fought with the utmost tenacity and stoutness.
The emperor of China, having received intelligence of what was going forward in the peninsula, had dispatched from Ap-lok-kong a general named Tso Shingfon at the head of a considerable force, to succor the Koreans. Yukinaga encountered this army and completely routed it, the Chinese general barely escaping with his life, the news of which event inspired much alarm in China. Kiyomasa, whose operations had also been attended with uniform success, now directed his forces southward, and Lien, the king of Korea, in his extremity, once more applied to China for aid. The Chinese sovereign thereupon commissioned a minister, Chom Wei-king, to consult with his colleagues as to the advisability of concluding peace with Japan. But among the Chinese captains there was one Li Chiu, who, having much confidence in his own prowess, insisted that no terms should be offered, and that the war should be prosecuted to the end. Another army was accordingly dispatched to Korea under his command, and marching with rapidity, he soon reached Hegushagu at the head of a great force. There he encountered the Japanese under Yukinaga and defeated them. Yukinaga retired to the Korean capital, whither also the other Japanese generals concentrated their troops, the corps under the command of Kobayagawa Takakage alone remaining to guard Kaijo, despite the urgent advice of the other three generals that he too should concentrate his forces at the capital. Li, following up his victory, pushed on toward the capital at the head of a large army. Takakage and others encountered the Chinese army at Hekitei-kan, and the divisions of Tachibana Muneshige and Mōri Hidekane fought with such bravery that Li's force was almost exterminated, Li himself barely escaping. Takakage hotly pursued the retreating Chinese, great numbers of whom either fell under the swords of the Japanese or were drowned in attempting to cross rivers. This blow threw the Chinese into a state of disorganization. Li retired into Hegushagu, and remained inactive.
Meanwhile, the victorious career of the Japanese had been checked in Chiushu, in attacking which place they were repulsed. Moreover, plague broke out in the camp and provisions were exhausted. Under these circumstances the Japanese were not unwilling to listen to proposals of peace made by a Chinese envoy, Chom Wei-king. Hideyoshi dictated seven articles as the basis of a treaty; first, that in order to secure amity between the two empires, a Chinese imperial princess should become the consort of a Japanese imperial prince: second, that permits for commercial intercourse should be sent to Japan; third, that the ministers of the two countries should exchange a friendly convention; fourth, that Korea should be divided into halves, one to belong to Japan, and the other, including the four provinces and the capital, then in Japanese hands, to be restored to Korea; fifth, that Korea should place in Japan's hands, as pledges of good faith, her prince royal and certain ministers of the crown; sixth, that Japan should restore to Korea the two Korean princes whom she had taken prisoners; and seventh, that influential Korean subjects should give written promises of submission to Japan. The Chinese envoy objected to the two conditions relating to the marriage of a Chinese princess with a Japanese prince, and to the partition of Korea. Hideyoshi, however, urged him to return to China and report the situation to his sovereign. Meanwhile, he ordered the Japanese generals to send back the two Korean prisoners, and to renew the attack on Chiushu, pending the conclusion of peace. But, after some further parleying, the Chinese envoy finally refused to comply with Hideyoshi's suggestion, and no answer to Japan's conditions was received from the Chinese emperor. Hideyoshi, now concluding that peace was impossible, began to make preparations for himself leading an army to attack China. At this juncture the envoy who had been sent to Japan, as well as other Chinese statesmen, suggested to their emperor that what Hideyoshi really wanted was an imperial commission appointing him king of Japan. The Chinese emperor accordingly dispatched another envoy to Japan carrying a gold seal and a headpiece specially manufactured for the purpose. In 1596, Hideyoshi gave audience to this envoy in the castle at Fushimi, and ordered him to read the documents with which he had come entrusted. The envoy complied, but when he came to the clause where it was stated that the Chinese government appointed Hideyoshi to be king of Japan, the taikō became greatly enraged. Seizing the document he threw it and the headpiece on the floor, and declared that his intention was to become king of China, and that the Chinese government should learn how little it had to do with the sovereignty of Japan. He dismissed the Chinese and Korean envoys, and issued orders for a campaign against China. In February of the following year, the Japanese generals assembled at Nagoya in Hizen, Kiyomasa and Yukinaga being the first to set out for Korea. The Chinese government, learning that the negotiations had been unsuccessful, sent another army to the peninsula under the command of Ying Kai and Tik Ho.
Meanwhile, the Korean general Li Shunshin had gained several victories over the Japanese forces, and joined by this new army, his strength became very great. Thereupon Kiyomasa fortified his position at Urosan, and there sustained a stubborn siege, the Chinese General Tik Ho's repeated efforts to reduce the place proving abortive. By degrees the provisions within Kiyomasa's lines became exhausted. His men were obliged to eat horse-flesh, and being exposed to the bitter cold of mid-winter many lost their hands from frost-bite. Hearing of the evil plight of their comrades, Toyotomi Hideaki and Mōri Hidemoto marched to the relief of Kiyomasa, and the besieging army retired without resistance. Kuroda Nagamasa fell on them as they retreated, and being joined by Kiyomasa, the two generals attacked the Chinese with great vehemence and completely routed them. Shimadsu Yoshihiro also defeated a Chinese army at Shinsai and Shisen. At this juncture, however, the taikō died. On the point of death he issued instructions for the recall of the Japanese army from Korea. This event occurred in 1598, and the news caused great rejoicing in China. The Chinese forces in Korea hung upon the flanks of the Japanese troops as they withdrew, but were so disheartened by the crushing reverses they had just experienced that they did not dare to make any serious attack. The Japanese ships also defeated the Chinese squadron, and were thus enabled to return to Japan unmolested. In the following year, the services of Tokugawa Iyeyasu and other Japanese generals were duly considered by the imperial court in Kyōto, and received adequate recognition. A few years later, in 1607, Korea sent an envoy to Japan carrying gifts and suing for peace. The Shōgun Tokugawa Hidetada received these overtures favorably and amicable relations were established between the two countries.