Lifespan: 15xx to third month of Tenshō 4 (1576)
Title: Master of the Outer Palace Guards of the Right Division
Father: Shiina Noritane
Wife: Koyomi (second daughter of Inami Shigechika)
Children: Shiina Kagenao (adopted from the Nagao clan of Echigo)
Shiina Yasutane served as a bushō during the Sengoku and Azuchi-Momoyama periods. Yasutane was a kokujin, or a member of an influential local family, and lord of Matsukura Castle in Etchū Province. Yasutane is surmised to be the son of Shiina Noritane.
Based in the Niikawa District, the Shiina clan held the status of deputy military governors of Etchū; however, after Noritane joined Jinbō Norimune in siding with the Etchū Ikkō-ikki against the Hatakeyama family (the military governors of Etchū), he lost the role of deputy military governor to the Nagao clan of Echigo. Although Noritane’s successor, Shiina Nagatsune, served as a vice-deputy military governor in service to the Nagao clan, following the death of Nagao Tamekage, the Shiina were attacked by Jinbō Nagamoto (who had succeeded in reviving the Jinbō clan), after which the Shiina clan declined in power. In the midst of these circumstances, Yasutane inherited the role as head of the Shiina family.
In 1557, during a period of internal discord within the Noto-Hatakeyama clan known as the Kōji Rebellion, Shiina Miyachiyo (may have been Yasutane) sent Yashiro Toshimori via sea route to provide support to Hatakeyama Yoshitsuna, a sengoku daimyō from Noto Province. Yoshitsuna later prevailed in the family dispute, serving to deepen the relationship with the Shiina clan.
In the summer of 1559, Jinbō Nagamoto pressed forward with another attack against the Shiina, so Yasutane requested reinforcements from Nagao Kagetora (later known as Uesugi Kenshin) of Echigo. In the third month of 1560, Toyama Castle and Masuyama Castle fell to the Uesugi forces, while Nagamoto fled. Having escaped from a crisis, later that same year, Yasutane participated in a deployment by Kagetora to the Kantō. However, Jinbō Nagamoto recovered his power and, on 9/5 of 1562, at the Battle of Jinzūgawa, the Shiina army suffered a major defeat including, among others, the loss of Jinzen Magogorō. The forces under Nagamoto proceeded to corner Yasutane at his base at Matsukura Castle (also known as Kanayama Castle). The next month, Kenshin came again in support of Yasutane and finally forced Nagamoto to surrender. The support provided by the Uesugi to the Shiina reflected the strong bonds between the clans after Yasutane adopted as a son a member of the Nagao family named Nagao Kagenao. Nevertheless, Yasutane was dissatisfied that the rights to govern the central portion of Etchū (the Nei and Imizu districts) were granted to his arch enemy – Jinbō Nagamoto of the Jinbō clan – through mediation by the Noto-Hatakeyama with whom the Jinbō had close relations.
While on his deployment to the Kantō, Kenshin took actions that demonstrated trust in Yasutane, such as assigning Yasutane to watch over his base at Kasugayama Castle. In the seventh month of 1568, Yasutane was lured by the Takeda to collude with them, rebelling against the Uesugi clan. In the eighth month of 1569, Kenshin responded to the separation by Yasutane by deploying to Etchū and surrounding Matsukura Castle. However, as a mountain fortress, the defenses were difficult to overcome, so, in the tenth month, the army lifted the siege and returned to Echigo. This was the first attempt by the Uesugi to capture the stronghold in the Siege of Matsukura Castle.
Thereafter, Yasutane reconciled with the Uesugi through the offices of Anegakōji Tsuguyori and dispatched reinforcements to the Hongan Temple in Ōsaka. In the fifth month of 1572, to support the western campaign by Takeda Shingen, Yasutane acted in concert with an attack by the Kaga Ikkō-ikki in Etchū, once again taking steps counter to the interests of the Uesugi. Consequently, after crushing the ikki forces, the Uesugi army surrounded Yasutane at Matsukura Castle again. In the first month of 1573, with Nagao Akikage (later known as Uesugi Kagekatsu) serving as an intermediary, Yasutane surrendered and vacated the castle. Thereafter, the whereabouts of Yasutane are unknown, but, according to one theory, in 1576, he was attacked while holed-up at Hasunuma Castle in the Tonami District (fighting for the ikki forces) by the Uesugi army and killed himself.