In the year 1592, Toyotomi Hideyoshi ordered Japanese samurai to invade China through Korea in order to establish an empire. However strange it may sounds, most of the warriors sent for this invasion were samurai from the Kato, Konishi, Kuroda, Ishida, Ukita, Shimazu, Mori and other Western samurai families, who were staunch supporters of the House of Toyotomi. Few of the samurai from the regions east of Kyoto such as Tokugawa Ieyasu and Date Masamune ever set foot to Korea and most of them were of dubious or questionable loyalty to Hideyoshi.
This unwise decision of Toyotomi Hideyoshi have undoubtedly sapped away the strength of those who would fight for the Toyotomi’s cause in future conflicts as about one third of those who embarked on this misadventure never made it back to Japan several years later.
To make matter worse, Toyotomi Hideyoshi ordered his nephew and heir apparent, Toyotomi Hidetsugu to commit suicide after Hidetsugu refused to lead the expedition to Korea. He even ordered Hidetsugu’s wife, mistresses, children, and retainers to be executed. Hideyoshi might have made this decision after his son, Hideyori was born to him in 1593. With this decision, only his young son would bear the Toyotomi’s family name after his demise. As long as Hideyoshi was alive, Tokugawa Ieyasu did not dare to challenge the House of Toyotomi.
In September 1598, Hideyoshi asked the Council of the Five Elders, namely Tokugawa Ieyasu, Mori Terumoto, Uesugi Kagekatsu, Maeda Toshie, and Ukita Hideie to come to his death bed and swear they would nurture his young son, Toyotom Hideyori until he came of age and that leadership would be passed to him. After the death of Toyotomi Hideyoshi, however, Ieyasu decided to claim power for himself.
Tokugawa Ieyasu began to gather allies with other daimyos. He had one of his sons to Date Masamune’s daughter while Fukushima Masanori’s son married one of Ieyasu’s daughters. He began to gather allies from the many powerful samurai families. Ieyasu had an advantage after Toyotomi Hideyoshi’s death, as the de facto leader of the pro-Toyotomi camp, Ishida Mitsunari was unpopular and disliked by many daimyos. Many of them joined Tokugawa camp, most notably Kato Kiyomasa and Kuroda Nagamasa. The son of Maeda Toshiie decided to join Tokugawa’s camp after the death of his father in the year 1599.
Soon, it was clear that a showdown between Tokugawa Ieyasu and the pro-Toyotomi camp was inevitable. The campaign began in earnest in the summer of year 1600 as skirmishes and minor battles broke out between the two rival forces. Ninjas broke into Tokugawa Ieyasu’s castle and unsuccessfully tried to assassinate Ieyasu. Ieyasu had been expecting this kind of assault have in fact managed to trap and killed all the assassins. The assassins were believed to be hired by Ishida Mitsunari, Ieyasu’s arch enemy.
The battle of Fushimi Castle epitomized a case of great loyalty when Torii Mototada and about 2,000 other Tokugawa warriors fought to the death against a much larger enemy force. They were all wiped out by their enemy. Torii Mototada’s death was said to have saddened Tokugawa Ieyasu greatly.
Another powerful daimyo, Hosokawa Tadaoki joined Tokugawa camp and Ishida’s warriors attacked his castle, causing the death of his wife, Hosokawa Gracia. When the castle was being attacked and set on fire, Gracia, the daughter of Akechi Mitsuhide (destroyer of Oda Nobunaga) asked a retainer to kill her. She did not commit suicide as her new religion, Christianity forbids suicide.
Tokugawa Ieyasu managed to persuade Kobayakawa Hideaki, a youthful general to betray Ishida Mitsunari during the imminent battle. Hideaki was known to harbor a grudge against Ishida Mitsunari as Mitsunari had told Toyotomi Hideyoshi about the reckless way Hideaki fought during a battle in the war against the Chinese and Korean forces during the Seven-Year War (1592 -1598) in Korea. Hideaki never forgot or forgave Mitsunari as Hideyoshi exiled Hideaki to another part of Japan as a punishment for his courageous but reckless method of fighting.