Battle of Odaihara

What Happened

On 19 September 1547, the army of Takeda Shingen (武田信玄) met and defeated the forces of Uesugi Norimasa (上杉憲政) at Odaihara, a post station in Shinano province (信濃国, Shinano no kuni). The Uesugi had marched out to relieve Shika Castle, which Shingen had placed under siege. Rather than wait for the relief force to reach the castle walls, Shingen intercepted it at Odaihara and broke it in the field.

The engagement was fought on open ground at a staging point on the road, not against a fortress. Shingen's commanders in the field included Itagaki Nobukata (板垣信方), Amari Torayasu (甘利虎泰) and Kanai Hidekage (金井秀景). The defeat of the relief force left the besieged castle without hope of rescue.

The battle belongs to the Tenbun era (天文, Tenbun), year 16 — the nengō (年号, era name) system by which years were counted in Japan until 1868. It falls within the Muromachi period (1336–1573) and within the longer stretch of civil war known as the Sengoku period (戦国時代, Sengoku jidai, "Warring States period").

Background

The Battle of Odaihara was one episode in Takeda Shingen's long campaign to conquer Shinano province. Shinano lay to the north of Shingen's home province of Kai (甲斐国, Kai no kuni) and was divided among a patchwork of local lords. Shingen's advance into Shinano drew in outside powers who did not want a single strong daimyō (大名, a territorial lord) controlling the province.

One of these was Uesugi Norimasa, whose base was Echigo province (越後国, Echigo no kuni) on the Japan Sea coast, north of Shinano. Norimasa chose to intervene in Shinano to stop Shingen from overrunning the whole province. The Uesugi army's objective in 1547 was to relieve Shika Castle, which Shingen had surrounded. The relief attempt brought the Uesugi force to Odaihara, where Shingen attacked it. The battle is counted as part of the wider Attack on Saku (佐久侵攻, Saku shinkō), Shingen's push into the Saku district of eastern Shinano.

Why It Mattered

Odaihara is a textbook example of how Shingen fought his way through Shinano: he besieged a castle, and when a relief army came, he destroyed the relief army rather than sitting passively around the walls. Beating the Uesugi in the open removed the only force capable of saving Shika Castle and demonstrated that intervention from Echigo could be met and defeated in Shinano itself.

The battle also belongs to the long, grinding contest between the Takeda and the Uesugi that would define the politics of central Japan for decades. Norimasa's intervention in 1547 was an early attempt to check Shingen's expansion; the Uesugi would remain Shingen's principal opponents in the region. For Shingen, the victory at Odaihara was one more step in the piecemeal absorption of Shinano, a province he spent years reducing castle by castle and district by district.

The Name in Japanese

The battle is written 小田井原の戦い and read おたいはらのたたかい (Otaihara no tatakai).

Breaking it down:

• 小 — read o here. Meaning: "small". It is normally read chii-sai or shō; in place names it very often appears as o.
• 田 — read ta here. Meaning: "rice field", "paddy". One of the most common elements in Japanese place names, reflecting the agricultural landscape the names grew out of.
• 井 — read i here. Meaning: "well" (a water well). Also common in place names, often in the sense of a settlement grouped around a well.
• 原 — read hara here. Meaning: "plain", "field", "open flat ground". A very frequent suffix in place names, describing level terrain.
• の — the hiragana particle no, the possessive/linking particle: "of", as in "the battle of Otaihara".
• 戦 — read tataka-i here (the verb stem tataka-u, "to fight", in its noun form). Meaning: "battle", "fight", "war". In formal compounds it is also read sen, as in 戦国 (sengoku, "warring states").
• い — the hiragana ending of the verb form tatakai, "a fight", written out rather than using the kanji alone.

So the name as a whole means "the Battle of Otaihara". Odaihara and Otaihara are both encountered in English writing; the kana reading given here is おたいはら. The place itself, Odai-juku (小田井宿), was a post station — a juku (宿) being a lodging stop on a highway where travellers and armies could rest and provision.

Key Figures

Takeda Shingen (武田信玄) — daimyō of Kai province and the driving force behind the campaign into Shinano. At Odaihara his army intercepted the Uesugi relief force and defeated it.

Uesugi Norimasa (上杉憲政) — based in Echigo province, he intervened in Shinano to prevent Shingen from taking the whole province. His army marched to relieve Shika Castle and was defeated at Odaihara on 19 September 1547.

Itagaki Nobukata (板垣信方) — one of Shingen's commanders present at the battle.

Amari Torayasu (甘利虎泰) — one of Shingen's commanders present at the battle.

Kanai Hidekage (金井秀景) — a commander present at the battle on the Takeda side.