Yoshimasa Koyama

Japanese: 小山義政 - おやま・よしまさ

Year of death: Eitoku 2/Kōwa 2.4.13 (1382.5.26)
Year of birth: Year of birth unknown. Military commander during the Northern and Southern Court period. Junior Fifth Rank, Lower Grade, Shimotsuke no Kami. Commonly known as Koshiro. He initially served as the guardian of Shimotsuke, and was the only person in Kanto, apart from the Uesugi clan, who frequently presented horses to the shogunate. However, as his territory expanded, he deepened conflict with the powerful Utsunomiya clan of Shimotsuke, and in May 1380, he killed Utsunomiya Mototsuna. Fearing that this would extend Yoshimasa's influence to northern Musashi and northwestern Shimousa, where the Kamakura shogunate was based, Kamakura kubo Ashikaga Ujimitsu immediately gathered a large army and attacked Oyama. Yoshimasa surrendered in September of the same year, but in February of the following year, 1381, he raised his army again. After fighting with the Kamakura shogunate forces at Oyama-Washi Castle for about six months, he became a monk in December, took the name Eiken, and surrendered. In March of the following year, he rebelled for the third time and took refuge in the mountains of Kasuo, but was defeated on April 13 and committed suicide. With the end of the Oyama Yoshimasa Rebellion, the Kamakura government's control of the Kanto region finally began to move in a more stable direction.

(Kazuo Matsumoto)

Source: Asahi Japanese Historical Biography: Asahi Shimbun Publications Inc. About Asahi Japanese Historical Biography

Japanese:

没年：永徳2/弘和2.4.13(1382.5.26)
生年：生年不詳
南北朝時代の武将。従五位下,下野守。通称小四郎。初め下野守護として活動し,上杉氏を除けば関東で唯一,度々幕府に馬を献上している。しかし領域拡大に伴い,下野の雄族宇都宮氏との対立を深め,康暦2/天授6(1380)年5月宇都宮基綱を討った。このことで義政の勢力が,鎌倉府の基盤とする武蔵北部,下総北西部におよぶことを恐れた鎌倉公方足利氏満は,直ちに大軍を集めて小山を攻める。同年9月義政は降伏するが,翌永徳1/弘和1(1381)年2月に再度挙兵。小山・鷲城において鎌倉府軍と約半年におよぶ戦闘を展開したのち,12月,出家して永賢と号し降参した。翌年3月,三度反抗し糟尾山中に籠城したが,4月13日敗れて自害した。この小山義政の乱の終息によって,鎌倉府の関東支配はようやく安定の方向に向かった。<参考文献>『小山市史』通史編Ⅰ

(松本一夫)

出典　朝日日本歴史人物事典：（株）朝日新聞出版朝日日本歴史人物事典について　情報

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