The siege of 鶴ヶ城 (Tsuruga-jo) — Wakamatsu Castle (若松城, Wakamatsu-jo), known as the Red Castle for its distinctive roof tiles — began on October 6, 1868, when Imperial forces surrounded the last great Tokugawa-loyal domain in northern Japan. The castle town of Aizu had always been different. Its lord, 松平容保 (Matsudaira Katamori), had served as Military Commissioner of Kyoto during the worst years of political violence that preceded the Meiji Restoration. He had tried to hold the old order together. Now the old order was gone, and Imperial troops were outside his walls.

Rumors swept through the town: all men would be killed. All women sold to Westerners. Whether those rumors were true hardly mattered. Thousands of people believed them.

The 白虎隊 (Byakkotai) had been formed in April 1868 — approximately 305 boys aged sixteen and seventeen, sons of Aizu samurai, organized as a reserve unit. A squad of twenty boys from the second group was separated from their unit during fighting at Tonoguchihara (戸ノ口原, Tonoguchihara) and retreated together to Iimori Hill. On October 8, they looked down at the valley below them and saw smoke filling the sky over the castle town.

What they could not see from the hill was the difference between the burning town and the castle at its center. The citadel was intact. The lord they served was alive. The domain had not yet surrendered. But nineteen of the twenty boys drew their blades and ended their lives in succession on the hill's wooded slope. The twentieth, 飯沼貞吉 (Iinuma Sadakichi), likely fourteen years old by Western reckoning, survived because his blade was dull and a local peasant found him before he could finish what he had started.

Sadakichi later served in the Sino-Japanese War, fought as a captain, and lived into the Meiji era — carrying the weight of Iimori Hill for the rest of his life. His account is why we know the story at all.

At Yanagi Bridge on October 16, 中野竹子 (Nakano Takeko) led a different kind of charge. Born in 1847, she was twenty-one years old and had trained in naginata since childhood. Senior retainers had refused to authorize female fighters, citing tradition and propriety. Takeko organized an unofficial corps of roughly twenty to thirty women — later called the 娘子隊 (Joshitai), or Girls' Army — and fought without permission.

Contemporary accounts describe her as a figure of startling intensity: "With her tied-back hair, trousers, and steely eyes, she radiated an intense male spirit and engaged the enemy troops." She killed five or six soldiers before Imperial troops, initially ordered not to shoot women, aimed and fired. The bullet struck her in the chest. Surrounded by battle, she asked her younger sister 竹子の妹 (Takeko no imōto) Yuko to behead her so that enemy soldiers could not take her head as a war trophy.

Her head was buried under a pine tree at 法界寺 (Hokai Temple). Her 薙刀 (naginata) was donated to the temple, where it remains on display.

The Aizu women's losses were staggering. When it became clear the castle could not hold, mass suicides swept through the domain. At the house of chief senior retainer 西郷頼母 (Saigo Tanomo) alone, twenty-one family members died — his wife Chieko killed their three youngest daughters with a sword before taking her own life. Teenage daughters, elder sisters, Tanomo's mother-in-law: all gone. Saigo Tanomo had been sent away to seek outside help. He returned to find his entire household dead.

Over 200 women and children died in this way during the siege and its immediate aftermath. A monument erected in 1928 commemorates 230 of them.

The castle surrendered on November 6, 1868. About 5,000 people eventually came out. 松平容保 (Matsudaira Katamori) was taken prisoner but his life spared; he spent years under house arrest before being appointed head priest of 日光東照宮 (Nikko Toshogu Shrine). For his retainers, the punishment was less gentle. In May 1869, chief retainer 権兵衛茅野 (Gombei Kayano) was sentenced to beheading with public head display. The survivors were relocated to the 斗南藩 (Tonami Domain) on the frozen Shimokita Peninsula in northern 青森 (Aomori) — barren, frigid land worth only 30,000 koku. Many elderly and children died of cold and hunger during the migration.

Accounts state that the Meiji government forbade proper burial rites for the dead of Aizu for six months after the surrender. The graves on Iimori Hill — nineteen stone markers for teenage boys, side by side on the wooded slope — were eventually permitted.

The story of Aizu became central to debates about Bushido in the Meiji era. Was this heroic loyalty or preventable tragedy? Nationalist Japan eventually lionized the Byakkotai; the American occupation, finding a Mussolini-era monument at Iimori Hill donated by Fascist Italy in admiration of the White Tiger boys, had it removed. The story remained contested: nineteen boys who died for a castle that was still standing, and a woman who fought harder than any official soldier, whose head is still buried under a pine tree in a temple on the outskirts of the city she died defending.