was a Japanese daimyō of the mid-Edo period, famous for his financial reforms which saved the Shirakawa Domain, and the similar reforms he undertook during his tenure as chief of the Tokugawa shogunate, from 1787 to 1793.
Early life
Matsudaira Sadanobu was the seventh son of Tokugawa Munetake, of the Tayasu branch of the Tokugawa clan. The Tayasu was one of the gosankyō, the senior-most of the lesser cadet branches of the Shōgun's family, and was thus the grandson of the reform-minded eighth shōgun Tokugawa Yoshimune. The Tayasu house stood apart from the other cadet branches resident in Edo Castle, living a more austere lifestyle, following the example set by Yoshimune—in Munetake's words, the praise of manly spirit (masuraoburi) as opposed to feminine spirit (taoyameburi). It also set itself apart from the other branches due to its history of thwarted political ambition—the founder, Munetake, had hoped to become his father's heir but was passed over for Yoshimune's eldest son, Tokugawa Ieshige. As a result, Sadanobu was brought up from a very young age with the hopes of being placed as the next shogunal heir, despite his poor health as a child. His education was very thorough, being done along Confucian lines, and by his teens Sadanobu had already read and memorized much of the Confucian canon. As he matured, there was a further onus on Sadanobu for success as several members of the Tayasu house began to die young. Further attempts were made by the family to place Sadanobu as the next shogunal heir, but they were thwarted by the political clique of Tanuma Okitsugu, who was then in power as the chief rōjū.
Early career
At the age of 17, he was adopted by Matsudaira Sadakuni, the daimyō of Shirakawa Domain in Mutsu Province, over the objections of the Tayasu clan, which was thus left without an heir. This issue arose the following year, and although Sadanobu petitioned to be reinstated with the Tayasu clan, Shogun Ieshige, at the instigation of Tanuma Okitsugu refused, and the clan remained without a leader for over a decade. In the meantime, Sadanobu succeeded to the head of the 100,000 koku Shirakawa Domain in late 1783 following his stepfather's protracted illness. He was immediately faced with his domain's economically disastrous position: of 110,000 koku that it was supposed to be able to produce, 108,600 had been reported "lost". Sadanobu worked ceaselessly to fix the economic situation in Shirakawa, finally saving it and bringing its finances and agriculture back to stability.
Sadanobu was also faced with issues caused by the Great Tenmei famine from 1782 to 1788. This had been caused by a combination of poor weather, volcanic eruptions and the mercantilist policy implemented by Tanuma Okitsugu intended to commercialize agriculture and thus increase tax income. Despite repeated failure of the rice crop, the government continued to insist on payment of taxes in rice, which led to famine in northern Japan, riots, and the bankruptcy of many of the northern domains. In previous famines, rice which had been stored in Edo had been used to provide famine relief, but under Tanuma, these reserves had already been sold off. Sadanobu prevented famine in Shirakawa by obtaining rice from Echigo Province and from Aizu Domain, which had been little affected by the crop failures, and earned great praise for his famine relief measures.
As Chief Councilor
These reforms, coupled with Sadanobu's continued political maneuvering, brought Sadanobu fame, and on the death of Tokugawa Ieharu, he was named chief councilor of the Shogunate in the summer of 1787, and regent to the 11th shōgun Tokugawa Ienari early the following year. He immediately started to use his position to overturn all of Tanuma Okitsugu's policies, and to revert to a system based on his grandfather's Kyōhō Reforms. Tanuma had attempted to stimulate the economy through mercantilist and capitalist policies, which Sadanobu felt had corrupted the samurai through the use of money and connections. In rural areas, the gap between rich and poor has become widespread, and poor farmers were fleeing the land for the cities, where they could make more money. As more farmland went uncultivated, famine forced more peasants into the cities, further disrupting social order. The Kansei Reforms aimed fiscal consolidation through severe austerity policies and sumptuary laws, rural reconstruction, and preventing the recurrence of popular uprising.
This period of Sadanobu's strengthening of the already faltering Tokugawa regime is known as the Kansei Reforms. His policies could as well be construed as a reactionary response to the excesses of his predecessor under Shōgun Ieharu.