Siege of Kinugasa Castle

What Happened

On 17 September 1180, forces of the Chichibu clan attacked Kinugasa Castle in Sagami Province, the stronghold of the Miura clan. The castle fell. The date is given in the Japanese reckoning as the fourth year of the Jishō era (治承, じしょう), on the twenty-sixth day of the eighth month.

Kinugasa Castle stood on a hill on the Miura Peninsula, in what is now Kinugasa Town in Yokosuka, Kanagawa Prefecture, at roughly 35.25° north, 139.65° east. The site overlooks the approaches to the peninsula and the sea lanes of Sagami Bay.

The assault was part of the Genpei War (源平合戦, げんぺいかっせん), the civil war between the Minamoto and Taira families for control of the imperial court and, ultimately, of Japan. The Miura had declared for the Minamoto. The Chichibu, who fought alongside the Taira, moved against them.

Among those caught in the fighting was Hatakeyama Shigetada, a warrior whose name is attached in the records both to this siege and to Kinugasa Castle itself. The castle's fall left the Miura position on the peninsula broken and scattered its survivors.

Background

The Genpei War began in 1180, the same year as the siege. Minamoto no Yoritomo, head of the Minamoto clan, raised arms against the Taira regime that had dominated the court since the 1150s. When Yoritomo's first bid for power collapsed at the Battle of Ishibashiyama in the eighth month of 1180, his supporters across the Kantō region were left exposed to Taira retaliation.

The Miura were one of the great warrior houses of Sagami Province, the coastal region south-west of modern Tokyo. They had thrown in with Yoritomo. That choice made them a target for the Taira and for the Kantō families who had sided with the Taira instead.

The Chichibu clan, based inland in the mountains of Musashi Province, were among those Taira-aligned houses. The encyclopedia summary of the battle also names the Edo clan among the Taira side, describing the Taira interest as operating through two branches, the Edo and the Chichibu. With Yoritomo's main force broken, the Chichibu could strike at his allies one by one. Kinugasa Castle was the Miura's principal fortification, and it was first on the list.

Why It Mattered

The siege was one engagement in a war that ran for five more years, and it ended in a defeat for the Minamoto side. Its importance lies in what it did to the Miura and to Yoritomo's network in the Kantō.

By taking Kinugasa Castle, the Chichibu stripped Yoritomo of a fortified base and a major allied house at the moment when his rebellion was at its weakest. The Miura were dispersed. For a time, the Taira and their Kantō allies held the initiative in Sagami.

The war did not end there. Yoritomo rebuilt his forces, and the Genpei War continued until the Taira were destroyed at the Battle of Dan-no-ura in 1185. The Miura re-emerged as one of the most powerful families of the Kamakura shogunate that Yoritomo founded. Kinugasa Castle stands in the record as the low point from which that recovery began.

The Name in Japanese

The Japanese name of the battle is 衣笠城合戦.

• Kana reading: きぬがさじょうかっせん
• Romaji: Kinugasa Jō Kassen

Broken down character by character:

衣 — read kinu here. It means "garment" or "robe." On its own the character is also read i or koromo.

笠 — read gasa here, a voiced form of kasa. It means "conical hat," the broad woven hat worn for shade or rain. Together, 衣笠 kinugasa means "robe and hat," and by extension a kind of umbrella-shaped covering. It is also a place name, and it names the hill on which the castle stood.

城 — read jō here (the character also has the native reading shiro). It means "castle." In Japanese place and castle names, 城 is the standard element for a fortified site.

合 — read kas in this compound, from kassen. It means "to join" or "to meet." Its most familiar use in this context is in 合戦 kassen, "battle."

戦 — read sen. It means "war," "battle," or "combat."

So 衣笠城合戦 is literally "Kinugasa Castle Battle": the name of the castle, 衣笠城, followed by 合戦, the standard word for a pitched battle. The reading of 合戦 is irregular — the two characters are read kassen, not by their ordinary on-readings — which is why the compound is worth learning as a single word. It appears constantly in accounts of the Genpei War and of medieval Japan generally.

Key Figures

Hatakeyama Shigetada — a warrior of the Kantō region whose name the records connect to the siege and to Kinugasa Castle. He is one of the figures associated with the defence of the castle.

The Miura clan — the warrior house of Sagami Province that held Kinugasa Castle. They had sided with Minamoto no Yoritomo, and the siege was fought against them.

The Chichibu clan — the Taira-aligned house that attacked the castle on 17 September 1180. The encyclopedia summary names them, along with the Edo clan, as the two branches through which the Taira interest in the region was pursued.

Minamoto no Yoritomo — head of the Minamoto clan and leader of the rebellion against the Taira. His defeat at Ishibashiyama in 1180 left his Kantō allies, the Miura among them, exposed to attack, and set the stage for the siege of Kinugasa Castle.