Japan is a long, narrow island nation from north to south, with many mountains and low plains. The largest and most fertile plain in Japan is the Kanto Plain. Plains are the most suitable for cultivation, which means higher cereal yields per unit area. In Japan's Sengoku period, the strength of a daimyō was measured by the grain output of his domain, that is, the stone high system. Roughly 10,000 stone territory can support about 300 samurai, and the territory of a daimyo with how many stones means that it can roughly mobilize troops.
Soon after Toyotomi Hideyoshi destroyed the Hojo clan in Kanto, Toyotomi Hideyoshi transferred Tokugawa Ieyasu's domain from mikawa and to the Kanto region, giving him more than 2.5 million stones in the Eight Prefectures of Kanto. On the eve of the Sekigahara War, the toyotomi clan's territory was only about 2.2 million stones. In addition, the territories of the Maori and Uesugi clans were both around 1.2 million, which was only half of tokugawa Ieyasu's power. Before Ieyasu was transferred, Ieyasu's territory was basically equivalent to that of the Maori and Uesugi clans.
It was Hideyoshi's transfer of Ieyasu to kanto that made Ieyasu the number one name in Japan after Hideyoshi's death. This was the most fundamental reason why Tokugawa Ieyasu was able to command the daimyō and eventually win the Battle of Sekigahara and win the world. So why did Toyotomi Hideyoshi transfer Tokugawa Ieyasu to the Kanto region so that he could flourish?
First of all, Toyotomi Hideyoshi's original intention in transferring to Tokugawa Ieyasu was out of distrust of Ieyasu, and wanted to move the hidden danger of Ieyasu away from him, so as to install the power of his cronies around him. Secondly, he wanted to use up Ieyasu's financial and material resources by removing the seal. However, Hideyoshi did not understand the importance of the Kanto, and eventually completed Tokugawa Ieyasu.
The indigenous people of the Kanto region were Ezo people, and during the shogunate period, the "Shogun of Seiyi", which refers to "Ezo". From the Kofun period to the Asuka period, the Yamato court continued to send troops to conquer this area. It was not until around 811 during the Heian period that the Yamato court established royal power in the Kanto region. The Yamato court always regarded the Kanto region as a barbaric and uncivilized land, and in order to strengthen the development of the Kanto region, the imperial court placed a large number of Watanabes (Chinese mainland and Koreans) here. Many of the princes who were demoted to vassal status were sent to administer the area and became local Hao clans (Genji, Heishi, etc.)
Since the Kanto region, considered by the Yamato Imperial Court to be conquered, taxes were always heavy and the local people were inferior. This was the "Pingjunmen Rebellion" that later had a very far-reaching impact. Seeing that the people of Kwantung were in deep trouble, and that the imperial court was extravagant and violent, he resolutely rebelled against the imperial court in his hometown of Shimoguni in 939, and eventually captured the Eight Kingdoms of Kanto, calling himself the "New Emperor", which was also the only person in Japanese history who openly opposed the imperial court and proclaimed himself emperor.
Although, the Pingjiangmen Rebellion was put down after only a few months. However, in order to quell the rebellion of the generals, the imperial court issued an edict to the world, and those who killed the generals were Zhu Zizhipin (five officials). This is epoch-making in Japanese history, which means that the local hao clan can also squeeze into the ranks of the nobility by virtue of their military achievements, and also open the bud of the samurai regime. In the end, it was also the Kanto local magnates Hirayoshi (Hei shomon's cousin) and Fujiwara Hidego who finally squeezed the ranks of the nobles in the Kanto region, and these two were finally squeezed into the ranks of nobles. Later, "Hei Kiyomori", a famous courtier in Japanese history and regarded as the originator of the samurai regime, was a descendant of Hira Sadamori.
The Kanto region was the birthplace of the Samurai of Japan and the center of the samurai regime that had always been under the rule of the samurai regime. The Genrai Dynasty, which founded the Kamakura shogunate, used Kamakura as its base to occupy the Kanto region, amassed power, and eventually destroyed the Hira clan and gradually unified Japan. The Muromachi shogunate did not set up a shogunate in the Kanto region, but it also set up a Kamakura gongfu in the Kanto region to rule the Kanto region. During the Sengoku period, the Hojo clan yasushi also relied on the fertile talents of the Kanto lands to stand on the feet of takeda Shingen and Uesugi Kenshin, two major military gods known as the Japanese Sengoku.
In Toyotomi Hideyoshi's mind, the traditional affluent and prosperous region was the most important. His direct packaging of the eight prefectures of Kanto to Ieyasu was a major mistake in seeing only the ruin and backwardness of the Kanto region, without fully recognizing the potential of the Kanto region.