Hisatoshi Isaku

...The Shimazu clan began to expand their influence in Hyuga Province in earnest during the reign of the brothers Motohisa and Hisatoyo, who advanced into San'in (the Ito clan's home base, the area east of the Tenjin ridge of Mt. Aoi, including the Miyazaki Plain, which was the territory of the Ito clan), and during the reign of Hisatoyo's son Tadakuni, in 1441 (Kakitsu 1), they forced Shogun Yoshinori's younger brother, Daikakuji Yoshiaki, who was accused of treason, to commit suicide at Kushima Eitokuji Temple, and received a reward from the shogunate. Tadakuni's son, Izaku Hisatoshi, was initially given the fief of Kushima, but in 1484 (Bunmei 16), he had a dispute with Niiro Tadatsugu of Obi, and Tadamasa, the son of Tadakuni's son, sent Hisatoshi back to Izaku and moved Tadatsugu to Shibushi, and gave Kushima and Obi to his relative, Tadanori (the Toyosu clan). However, they came into conflict with the Ito clan, who had been eyeing Obi for some time, and the region was the subject of repeated struggle between the two clans for a long time.

*Some of the terminology that refers to "Isaku Hisaichi" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…島津氏が本格的に日向国に勢力を伸ばしたのは元久･久豊兄弟の代で，伊東氏領の宮崎平野も併せ山東(青井岳天神嶺以東の地，伊東氏の本拠)に進出，久豊の子忠国の代には，1441年(嘉吉1)謀叛の罪に問われた将軍義教の弟大覚寺義昭を櫛間永徳寺に自刃させ，幕府より恩賞を受けている。忠国の子伊作久逸（いざくひさとし）ははじめ櫛間に封じられたが，84年(文明16)飫肥（おび）の新納忠続と争い，忠国の子立久の子忠昌は久逸を伊作に帰し，忠続を志布志に移し，一族の忠廉(豊州家)に櫛間，飫肥を与えている。しかしかねてより飫肥をうかがっていた伊東氏と衝突し，同地方は以来久しく両氏が争奪をくりかえした。…

※「伊作久逸」について言及している用語解説の一部を掲載しています。

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