Battle of Aizu

What Happened

The Battle of Aizu (会津戦争, Aizu sensō) was fought in northern Japan in the autumn of 1868, part of the Boshin War. The fighting is dated to 6 November 1868, and it ranged across the Aizu region of northern Honshu, around coordinates 37.30°N, 139.56°E. It pitted the forces of Aizu Domain against the imperial army, and it ended in the defeat of Aizu.

The campaign was not a single engagement but a cluster of them. The Battle of Noheji, the Battle of Bonari Pass, the Battle of Shirakawa, the Battle of Nihonmatsu, the Battle of Iwaki, and the Battle of Mikuni Pass all belong to this wider operation, and the Siege of Aizu Castle was its decisive episode. Bonari Pass opened the road into Aizu territory; once the pass fell, the imperial columns could descend on the Aizu basin. Nihonmatsu, a castle town to the east, was taken before the advance reached Aizu-Wakamatsu itself.

The siege of Aizu Castle drew in a wide cast. Ōtori Keisuke, Saigō Tanomo, Dewa Shigetō, Yamakawa Kenjirō, and Beppu Shinsuke are all recorded in connection with the conflict, alongside Aizu Domain itself. The fighting ended with Aizu's surrender in the eleventh month of 1868, closing one of the last great campaigns of the Boshin War.

Background

The Boshin War grew out of the collapse of the Tokugawa shogunate. In 1867 the shogun Tokugawa Yoshinobu returned political authority to the imperial court, and in early 1868 the new imperial government moved against him. The opening clashes of the war took place far to the south and west, around Kyoto and then in the Kantō plain. When the shogunal cause lost those battles, its surviving supporters pulled back north and east.

Aizu was one of the great domains of northern Japan and had been a loyal ally of the Tokugawa house for centuries. Its lords were bound to the shogunate by long service, and when the shogunate fell, Aizu became a natural rallying point for those who refused to accept the new order. A northern coalition of domains, sometimes called the Northern Alliance, formed around this resistance. The imperial army, advancing up the main roads from the south, had to break that coalition to end the war.

The approach to Aizu ran through a series of mountain passes and castle towns. Bonari Pass and the Shirakawa barrier controlled the southern entrances to the region; Nihonmatsu lay on the road beyond. Each of these positions had to be reduced in turn, which is why the campaign reads as a sequence of named battles rather than one field engagement.

Why It Mattered

The defeat of Aizu removed the strongest military pillar of resistance to the new Meiji government in northern Japan. With Aizu broken, the remaining holdouts in the north lost their base and their principal ally, and organised shogunal resistance on Honshu came to an end. The war would continue briefly in the far north of Honshu and on Hokkaido, but the outcome was no longer in doubt.

The campaign also became one of the founding stories of modern Japan. Aizu's young warriors, organised into a unit known as the Byakkotai, are remembered for their deaths during the fighting around the castle. Their fate turned Aizu into a byword for loyalty to a lost cause, and the domain's defeat shaped the politics of the new era: men from the victorious domains of Satsuma and Chōshū dominated the Meiji government for decades, while Aizu survivors and their descendants carried the memory of 1868 with them.

The battle falls in the first year of the Meiji era, which gives it a particular place in the chronology. The era name changed in 1868, the same year the fighting took place, so the Battle of Aizu sits exactly on the line between the Tokugawa order and the Meiji state.

The Name in Japanese

The Japanese name is 会津戦争. It is read あいづせんそう in kana, and written Aizu sensō in romaji. The word breaks into three kanji.

会 — read ai here. The character means "to meet" or "meeting". In this name it is not used for its meaning but purely for its sound, as the first element of the place name Aizu.

津 — read zu here. The character means "harbour" or "crossing", and it appears in many Japanese place names. As with 会, it functions here as part of the place name rather than as an independent word. Note that the reading is zu, not tsu: the two characters together are read Aizu, with the t of tsu voiced between vowels.

戦 — read sen. The character means "war" or "battle". It is the standard kanji for armed conflict and appears in compounds such as 戦争 (sensō, war) and 戦場 (senjō, battlefield).

争 — read sō. The character means "strife", "dispute", or "contention". Combined with 戦, it forms 戦争 (sensō), the ordinary Japanese word for "war". The compound 戦争 is stronger than 戦 alone: 戦 can mean a single battle, while 戦争 means a war as a whole.

So 会津戦争 is literally "the Aizu war" — the war of, or at, Aizu. The same place name appears in 会津若松 (Aizu-Wakamatsu), the castle town at the centre of the campaign, and in 会津藩 (Aizu-han), Aizu Domain.

Key Figures

Ōtori Keisuke — a shogunal official and military leader who continued to fight for the Tokugawa cause after the fall of the shogunate, and who is recorded in connection with the Aizu conflict.

Saigō Tanomo — an Aizu retainer associated with the domain's service and its conduct during the war.

Dewa Shigetō — recorded among those connected with the conflict; he later became a prominent figure in the Meiji-era navy.

Yamakawa Kenjirō — a native of Aizu who lived through the campaign as a young man and went on to a distinguished career in Meiji science and education.

Beppu Shinsuke — a samurai of the shogunal forces, recorded in connection with the Aizu conflict.

Aizu Domain — the domain itself, whose forces and castle were at the centre of the campaign.