His health beginning to falter, but still yearning for some accomplishment to solidify his legacy, Hideyoshi adopted the dream of a Japanese conquest of China that Oda Nobunaga had contemplated, and launched two ill-fated invasions of Korea. Though he actually intended to conquer Ming China, Hideyoshi had been communicating with the Koreans since 1587 requesting unmolested passage into China. As vassal of Ming China, the Koreans at first refused talks entirely, and in April and July 1591 refused demands that Japanese troops be allowed to march through Korea. The Koreans were also concerned that allowing Japanese troops to march through Korea (Joseon) would mean that masses of Ming Chinese troops would battle Hideyoshi's troops on Korean soil before they could reach China¡ªeffectively ruining the Joseon economy. In August, Hideyoshi ordered preparations for invasion. Under Chinese tributary system, Korean aristocrats (Yangban) were devoted to factional disputes in politics. While Japan was preparing war, Korea was not alarmed at all.
In the first campaign, Hideyoshi appointed Ukita Hideie to the field marshal, and had them go to the Korean peninsula in April, 1592. Konishi Yukinaga occupied Seoul which had been the capital of Joseon Dynasty Korea on May 10. After Seoul fell easily, Japanese commanders held a war council in June in Seoul and determined targets of subjugation called Hachidokuniwari (literally, dividing the country into eight routes) by each corps (the First Division of Konishi Yukinaga and others from Pyeongan Province, the Second Division of Kato Kiyomasa and others from Hangyong Province, the Third Division of Kuroda Nagamasa and others from Hwanghae Province, the Forth Division of Mori Yoshinari and others from Gangwon Province; the Fifth Division of Fukushima Masanori and others from Chungcheong Province; the Sixth Division by Kobayakawa Takakage and others from Jeolla Province, the Seventh Division by M¨ri Terumoto and others from Gyeongsang Province, and the Eighth Division of Ukita Hideie and others from Gyeonggi Province). and in only four months, Hideyoshi's forces had a route into Manchuria and occupied much of Korea. Korean king Seonjo of Joseon escaped to Uiju, and requested military intervention from China. In 1593, Ming Chinese Emperor Wanli sent an army under general Li Rusong to block the planned invasion of China and recapture the Korean peninsula. the Ming Army of 43,000 soldiers headed by Li Ru-song attacked Pyongyang. On January 7, 1593, the Chinese relief forces under Li eventually recaptured Pyongyang, and surrounded Seoul, but Kobayakawa Takakage, Ukita Hideie, Tachibana Muneshige and Kikkawa Hiroie, won the Battle of Byeokjegwan in the suburbs of Seoul.
The birth of Hideyoshi's second son, Hideyori, in 1593 created a potential succession problem. To avoid it, Hideyoshi exiled his nephew and heir Hidetsugu to Mount Koya and then ordered him to commit suicide in August 1595. Hidetsugu's family members who did not follow his example were then murdered in Kyoto, including 31 women and several children.
On February 5, 1597, Toyotomi Hideyoshi had twenty-six Christians killed as an example to Japanese who wanted to convert to Christianity. They are known as the Twenty-six Martyrs of Japan. They included five European Franciscan missionaries, one Mexican Franciscan missionary, three Japanese Jesuits and seventeen Japanese laymen including three young boys. They were executed by public crucifixion in Nagasaki.
After several years of negotiations (broken off because envoys of both sides falsely reported to their masters that the opposition surrendered), Hideyoshi appointed Kobayakawa Hideaki to lead the invasion forces, but their efforts on the Korean peninsula met with less success than the first invasion. Japanese troops remained pinned in Gyeongsang province. By June 1598, The Japanese forces fought with desperation, turning back several Chinese offensives in Suncheon and Sacheon as the Ming army prepared for a final assault. The Koreans guerrilla warfare, aided by the fact that they were fighting on their homeland, continually harassed Japanese forces. While Hideyoshi's last battle at So-chon, was a major Japanese victory, all three parties to the war were exhausted. and Hideyoshi himself now accepted that the war could not be won. He told his commander in Korea: "Don't let my soldiers become spirits in a foreign land.", Toyotomi Hideyoshi died September 18, 1598 of complications caused by the bubonic plague. His death was kept secret by the Council of Five Elders to preserve morale, and Japanese troops were withdrawn from the Korean peninsula.
Because of his failure to capture Korea, Hideyoshi's forces were unable to invade China. Rather than strengthen his position, the military expeditions left his clan's coffers and fighting strength depleted, his vassals at odds over responsibility for the failure, and the clans that were loyal to the Toyotomi name weakened. The dream of a Japanese empire encompassing Asia ended with Hideyoshi. The Tokugawa government not only prohibited any military expeditions to the mainland, but closed Japan to nearly all foreigners during the years of the Tokugawa Shogunate. It was not until the late 19th century that Japan again fought a war against China through Korea, using much the same route that Hideyoshi's invasion force had used.
After his death, the other members of the Council of Five Regents were unable to keep the ambitions of Tokugawa Ieyasu in check. Two of Hideyoshi's top generals Kat¨ Kiyomasa and Fukushima Masanori had fought bravely during the war, but returned to find the Toyotomi clan castellan Ishida Mitsunari in power. He held the generals in contempt, and they sided with Tokugawa Ieyasu. Hideyoshi's underaged son and designated successor Hideyori lost the power his father once held, and Tokugawa Ieyasu was declared Shogun following the Battle of Sekigahara.
Toyotomi Hideyoshi changed Japanese society in many ways. These include imposition of a rigid class structure, restriction on travel, and surveys of land and production.
Class reforms affected commoners and warriors. During the Sengoku period, it had become common for peasants to become warriors, or for samurai to farm due to the constant uncertainty caused by the lack of centralized government and always tentative peace. Upon taking control, Hideyoshi decreed that all peasants be disarmed completely. Conversely, he required samurai to leave the land and take up residence in the castle towns. This solidified the social class system for the next 300 years.
Furthermore, he ordered comprehensive surveys and a complete census of Japan. Once this was done and all citizens were registered, he required all Japanese to stay in their respective han (fiefs) unless they obtained official permission to go elsewhere. This ensured order in a period when bandits still roamed the countryside and peace was still new. The land surveys formed the basis for systematic taxation.
In 1590, Hideyoshi completed construction of the Osaka Castle, the largest and most formidable in all Japan, to guard the western approaches to Kyoto. In that same year, Hideyoshi banned "unfree labor" or slavery; but forms of contract and indentured labor persisted alongside the period penal codes' forced labor.
Hideyoshi also influenced the material culture of Japan. He lavished time and money on the tea ceremony, collecting implements, sponsoring lavish social events, and patronizing acclaimed masters. As interest in the tea ceremony rose among the ruling class, so too did demand for fine ceramic implements, and during the course of the Korean campaigns, not only were large quantities of prized ceramic ware confiscated, many Korean artisans were forcibly relocated to Japan.
Inspired by the dazzling Golden Pavilion in Kyoto, he also constructed a fabulous portable tea room, covered with gold leaf and lined inside with red gossamer. Using this mobile innovation, he was able to practice the tea ceremony wherever he went, powerfully projecting his unrivaled power and status upon his arrival.
Politically, he set up a governmental system that balanced out the most powerful Japanese warlords (or daimyo). A council was created to include the most influential lords. At the same time, a regent was designated to be in command.
Just prior to his death, Hideyoshi hoped to set up a system stable enough to survive until his son grew old enough to become the next leader. A Council of Five Elders was formed, consisting of the five most powerful daimyo. Following the death of Maeda Toshiie, however, Tokugawa Ieyasu began to secure alliances, including political marriages (which had been forbidden by Hideyoshi). Eventually, the pro-Toyotomi forces fought against the Tokugawa in the Battle of Sekigahara. Ieyasu won and received the title of Seii-tai Shogun two years later.
Hideyoshi is commemorated at several Toyokuni Shrines scattered over Japan.
Ieyasu left in place the majority of Hideyoshi's decrees and built his shogunate upon them. This ensured that Hideyoshi's cultural legacy remained. In a letter to his wife, Hideyoshi wrote:
I mean to do glorious deeds and I am ready for a long siege, with provisions and gold and silver in plenty, so as to return in triumph and leave a great name behind me. I desire you to understand this and to tell it to everybody."