Lifespan: 8/23 of Kyōroku 4 (1531) to 11/3 of Eiroku 8 (1565)
Other Names: Tokujumaru (childhood), Jirō, Yoshiyori
Rank: sengoku daimyō
Title: Master of the Western Capital Office
Father: Satake Yoshiatsu
Mother: Daughter of Oda Shigeharu
Siblings: Yoshitomo, Yoshiaki, Yoshishige, Yūgi (monk at the Kōmyō Temple), Sūtetsu (monk at the Shōjū Temple), Kikujumaru, Onosaki Yoshimasa (Daijō Masamoto), sister (wife of Ishizuka Yoshinori), sister (wife of Ōyama Yoshikage)
Wife: [Formal] Daughter of Iwaki Shigetaka, [Second] Daughter of Daijō Norimoto
Children: Yoshishige, Nasu Sukeie, Yoshihisa, Oba Yoshimune, Nanryoin (wife of Utsunomiya Hirotsuna), Keijuin (wife of Iwaki Chikataka)
Satake Yoshiaki served as a sengoku daimyō and the seventeenth head of the Satake clan based at Ōta Castle in Hitachi Province.
On 8/23 of Kyōroku 4 (1531), Yoshiaki was born as the second son of Satake Yoshiatsu, the sixteenth head of the Satake clan. His older brother of a different mother, Satake Yoshitomo, was an illegitimate child so Yoshiaki was designated the heir to the clan.
In 1545, following the death of his father, Yoshiaki inherited the headship of the clan and became its seventeenth head. Around this time, the clan brought internal troubles under control while Yoshiaki grew into a sengoku daimyō governing the northern portion of Hitachi. As a result, he expanded his authority with the aim of unifying the entire province.
Together with Oda Masaharu, he fought against and defeated Edo Tadamichi. In 1557, after an internal conflict erupted in the Utsunomiya clan, Yoshiaki cooperated with Utsunomiya Hirotsuna to enable his return to Utsunomiya Castle. Later, Yoshiaki wed his daughter to Hirotsuna. In 1558, when Iwaki Shigetaka invaded Hitachi, Yoshiaki defeated him at Ozato. He then entered into a favorable settlement for the purposes of establishing a political alliance through marriage between the clans. In 1560, Yoshiaki attacked and prevailed against Yūki Harutomo and then assaulted Yūki Harutsuna at Terayama Castle. In 1562, Yoshiaki entered into an alliance with Uesugi Terutora (later known as Uesugi Kenshin) and attacked Oyama Castle in Shimotsuke Province. In this year, he transferred headship of the clan to his eldest son, Satake Yoshishige, retired, and moved to Fuchū in Hitachi. Nevertheless, he continued to maintain his grip on power.
In 1563, he defeated Nasu Suketane in battle. In 1564, Yoshiaki incurred an attack by Hōjō Ujiyasu and the joint forces of Yūki Harutomo and Oda Ujiharu, but Yoshiaki allied with Uesugi Kenshin and Utsunomiya Hirotsuna to invade the territory of the Oda and capture Oda Castle, pursuing Ujiharu to Tsuchiura Castle in the Niihari District of Hitachi. This event is known as the Battle of Sannōdō. Furthermore, he intervened in the Daijō clan (the original family of his second wife) and placed them under his de facto command.
On 11/3 of Eiroku 8 (1565), while on the verge of unifying Hitachi, Yoshiaki suddenly died at the age of thirty-five. Consequently, the Satake fell one step short of fulfilling Yoshiaki’s aim to unify the province.
Yoshiaki was succeeded by his eldest son, Satake Yoshishige, the eighteenth head of the Satake clan.
Anecdotes and Character
In 1546, during the Siege of Kawagoe Castle, Uesugi Norimasa, the deputy shōgun of the Kantō, suffered a major defeat. At the time, Norimasa sought the protection of Yoshiaki (who was rapidly expanding his power in Hitachi) in exchange for allowing Yoshiaki to succeed to the family name of the Yamauchi-Uesugi and the role of the deputy shōgun of the Kantō. Dating back to 1407, Satake Yoshihito became the twelfth head of the Satake clan through adoption from the Yamauchi-Uesugi clan. Henceforth, the Satake were descendants of the Uesugi on the paternal side of the family. While Yoshiaki was interested in the hereditary role of the deputy shōgun of the Kantō, on the maternal side of the family, the Satake had the status of being descendants of Minamoto no Yoshimitsu of the Seiwa-Genji. This may have been the reason why Yoshiaki finally rejected adoption of the family name of the Yamauchi-Uesugi.
The reasons for his early retirement are unclear, but, given that he died at the age of thirty-five, it is surmised he had frail health.