Hirai Castle

Japanese: 平井城 - ひらいじょう

Hirayama-jiro (Hirayama Castle) was located in Fujioka City, Gunma Prefecture during the Warring States Period. It is a designated historic site by the prefecture. It was the final castle of the Yamauchi Uesugi clan, the Kanto Kanrei family. It was built on a cliff on the left bank of the Ayukawa River in the Hirai district of the city. It is said that Kanto Kanrei Yamauchi Uesugi Norizane, who fled to Kozuke Province in conflict with Kamakura kubo Ashikaga Mochiuji during the Eikyō Rebellion that occurred in 1438 (Eikyō 10), ordered his senior vassal Nagao Tadafusa (the head of the Nagao clan) to build it, but there are various theories about when and who built the castle. Later, in 1467 (Onin 1), Kanto Kanrei Uesugi Akisada carried out extensive renovations of the castle and established the Kanto Kanrei government office there. From then on, it became the castle of the Yamauchi Uesugi clan, who held the position of Kanto Kanrei until Uesugi Norimasa. In 1545 (Tenbun 14), Norimasa, along with Ogigayatsu-Uesugi Tomosada and Koga-kubo Ashikaga Haruuji, led an army of 80,000 men to besiege the Hojo clan's Kawagoe Castle (Kawagoe Castle, Saitama Prefecture). However, in April of the following year, they were destroyed by a surprise attack by Hojo Ujiyasu, who had a small force, and Ogigayatsu-Uesugi Tomosada was killed in battle, and Norimasa fled to Hirai Castle. In the Battle of Odaibaru the following year, Norimasa was defeated by Takeda Harunobu (later known as Takeda Shingen), causing his power to rapidly decline. In 1551 (Tenbun 20), when Hojo Ujiyasu set out to attack Hirai Castle with an army of 20,000 men, Norimasa abandoned the castle and fled to Echigo, relying on Nagao Kagetora (later known as Uesugi Kenshin) at Kasugayama Castle (Joetsu City, Niigata Prefecture). His eldest son, Tatsuwakamaru, remained in Hirai Castle, but surrendered and opened the castle to the Hojo clan. Hojo Ujiyasu, who occupied the castle, appointed his uncle, Hojo Genan Nagatsuna, as the lord of Hirai Castle. Hirai Castle was later recaptured by Nagao Kagetora, but when Kagetora marched to Kanto in 1560 (Eiroku 3), he used Umabashi Castle (Maebashi City) as his base in the Kanto region, and Hirai Castle was abandoned. Currently, the castle ruins are maintained as Kanto Kanrei Hirai Castle Ruins Park, and the earthworks, inner moat, and bridges have been restored. Hirai Kanayama Castle, located in the southwest of the castle, was the rear castle of Hirai Castle. Take the bus from Gunma Fujioka Station on the JR Hachiko Line to Nishihirai, and walk for 1 minute.

Source: Kodansha Encyclopedia of Japanese Castles Information

Japanese:

群馬県藤岡市にあった戦国時代の平山城(ひらやまじろ)。同県指定史跡。関東管領家の山内上杉氏の最後の居城。同市平井地区の鮎川左岸の断崖上に築かれていた。1438年（永享10）に起こった永享の乱で、鎌倉公方足利持氏と対立して上野国に逃れた関東管領の山内上杉憲実が、重臣の長尾忠房（総社長尾氏）に命じて築かせたともいわれるが、築城時期・築城者については諸説ある。その後、1467年（応仁1）に、関東管領の上杉顕定が城の大改修を行い、関東管領府を置いた。以後、上杉憲政に至るまで関東管領職を継いだ山内上杉氏の居城となった。1545年（天文14）、憲政は扇谷上杉朝定、古河公方足利晴氏らとともに8万ともいわれる軍勢で、北条氏の川越城（河越城、埼玉県川越市）を包囲したが、翌年4月の川越野戦において小勢の北条氏康の奇襲攻撃を受けて壊滅、扇谷上杉朝定は戦死し、憲政は平井城に逃れた。その翌年の小田井原の戦いでも武田晴信（のちの武田信玄）に大敗して勢力を急速に衰えさせ、1551年（天文20）に北条氏康が2万の軍勢で平井城攻略に乗り出すと、憲政は同城を捨て春日山城（新潟県上越市）の長尾景虎（のちの上杉謙信）を頼って越後に脱出。平井城には嫡男龍若丸が残ったが、北条氏に降伏・開城した。城を占領した北条氏康は叔父の北条幻庵長綱を平井城主としている。その後、長尾景虎により平井城は奪還されたが、1560年（永禄3）に景虎が関東に出陣した際、厩橋城（前橋市）を関東における拠点としたことから、平井城は廃城となった。現在、城跡は関東管領平井城趾公園として整備され、土塁や内堀、橋などが復元されている。同城の南西部にある平井金山城は、平井城の詰めの城である。JR八高線群馬藤岡駅からバスで西平井下車、徒歩1分。

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