Gosannen War

What Happened

The Gosannen War (後三年の役, gosannen no eki) was fought in Mutsu Province (陸奥国, Mutsu no kuni) in the far north-east of Honshū between 1083 and 1087. It was a civil war within a single warrior family, the Kiyohara (清原), over who would control the province. The fighting drew in Minamoto no Yoshiie (源義家), a celebrated warrior from the capital, and ended with the rise of Fujiwara no Kiyohira (藤原清衡), who would build an independent power base in the north.

The war began in 1083 as a dispute among the Kiyohara. Kiyohara no Iehira (清原家衡) and his kinsman 清原武衡 (Kiyohara no Takehira) were among the combatants. Minamoto no Yoshiie intervened in the conflict. The war lasted four years and was fought out at fortified positions in Mutsu, including the Kanezawa Palisade (金沢柵, Kanezawa no saku) and the Numa Palisade (沼柵, Numa no saku). The conflict ended in 1087 with the defeat of Iehira and Takehira and the establishment of Fujiwara no Kiyohira as the dominant figure in the region.

Background

The Gosannen War followed an earlier northern conflict, the Zenkunen War (前九年の役, zenkunen no eki), which had also been fought in Mutsu. The two wars are treated as a pair: the Zenkunen War came first, and the Gosannen War followed it. Both were fought during the Heian period (平安時代, Heian jidai), the long era from 794 to 1185 when the imperial court sat in Kyoto and the provinces were governed at a distance by local magnates and warrior houses.

Mutsu Province lay at the northern edge of the territory controlled from Kyoto. Its distance from the capital gave local families room to build their own armed followings and to settle disputes by force. The Kiyohara were one such family. The war of 1083 to 1087 was fought over the succession to that local power, and the intervention of Minamoto no Yoshiie, a member of the Minamoto warrior house, turned a provincial quarrel into a campaign that drew the attention of the court.

The war began in the third year of the Eihō era (永保, Eihō), a nengō (年号, nengō) or era name used to count years under the Heian court's system of dating.

Why It Mattered

The war ended with Fujiwara no Kiyohira in control of Mutsu. Kiyohira went on to found a line that governed the north for generations, the Ōshū Fujiwara (奥州藤原), based at Hiraizumi. The northern realm they built was wealthy and largely independent of Kyoto, and it lasted until the end of the twelfth century.

The war also made the reputation of Minamoto no Yoshiie. His intervention in a distant provincial quarrel, and his conduct of the campaign, became part of the warrior legend that later shaped the self-image of the Minamoto house. The conflict is remembered as one of the two great northern wars of the Heian period, paired with the Zenkunen War that preceded it.

The Name in Japanese

The Japanese name is 後三年の役. Its kana reading is ごさんねんのえき, and its romaji is gosannen no eki. The same conflict is also called 後三年合戦 (ごさんねんかっせん, gosannen kassen), "the Later Three-Year Battle". The English name "Gosannen War" is a direct rendering of the Japanese.

Character by character:

• 後 — read here as ご (go). It means "after", "later" or "behind". In this name it marks the war as the later of two conflicts.
• 三 — read here as さん (san). It means "three".
• 年 — read here as ねん (nen). It means "year".
• の — read as の (no). The possessive and linking particle, written in kana rather than kanji. It joins "Gosannen" to "eki".
• 役 — read here as えき (eki). It means "war", "campaign" or "service". In historical names it labels a military conflict.

The first three characters together, 後三年, mean "the later three years". The name is a matching pair with the earlier war, the Zenkunen War, whose Japanese name is 前九年の役 (ぜんくねんのえき, zenkunen no eki): 前 (ぜん, zen) means "before" or "earlier", and 九 (く, ku) means "nine". So the two wars are named as "the Earlier Nine Years" and "the Later Three Years". The numbers refer to the length of the campaigns as the chronicles counted them, not to the calendar years in which they were fought.

A reader meeting the name in a Japanese text should note two things. First, 後三年 is read ごさんねん, not with the ordinary readings of 後 and 年 alone; the whole phrase is a set name. Second, 役 in this context is えき, not the everyday reading やく. The word 合戦 (かっせん, kassen), "battle", appears in the alternative name and is a common element in the names of Japanese wars.

Key Figures

Minamoto no Yoshiie (源義家) — a warrior of the Minamoto house who intervened in the Kiyohara dispute and fought through the campaign of 1083 to 1087. His conduct in the north became central to his reputation.

Fujiwara no Kiyohira (藤原清衡) — the figure who emerged from the war in control of Mutsu. He founded the northern Fujiwara line that ruled from Hiraizumi.

Kiyohara no Iehira (清原家衡) — a member of the Kiyohara family and one of the combatants in the civil war over the province. He was defeated by the war's end in 1087.

清原武衡 (Kiyohara no Takehira) — a Kiyohara kinsman who fought alongside Iehira and was likewise defeated in 1087.