Snow at Sakuradamon: The Assassination That Ended the Bakufu

The Sakuradamon Incident of March 24th, 1860 was the political assassination that, more than any other single event of the Bakumatsu, marked the beginning of the end of the Tokugawa Bakufu. The man who died was the Tairō (Great Elder) Ii Naosuke, the most senior official of the bakufu's central administration. The men who killed him were eighteen ronin from the Mito and Satsuma domains. The location was the main gate of Edo Castle — the symbolic heart of the bakufu — on a snow-covered morning when Ii's procession was making its way to a routine policy meeting.

The incident lasted approximately seven minutes. Its political effects worked out over the next eight years and ended in the Meiji Restoration. The killing made it clear that the bakufu could not protect even its own most senior official within sight of its central building. Once that fact was known, the bakufu's ability to enforce decisions decayed continuously.

Who Ii Was

Ii Naosuke had become Tairō in 1858, an unusual circumstance under which the Tokugawa elevated him from the daimyō of Hikone to the de facto head of the bakufu's executive council. The elevation was driven by the foreign-treaty crisis — the Americans had arrived demanding open ports in 1853, the British and French were following, and the bakufu was paralyzed by the divide between officials who wanted to negotiate and officials who wanted to refuse. Ii was a negotiator. He believed the bakufu could not realistically resist the Western fleets and that signing acceptable treaties was the only practical option.

His two defining decisions in office were both inflammatory. First, in July 1858, he signed the Harris Treaty with the United States — the so-called 'unequal treaty' that opened five Japanese ports to American trade — without obtaining sanction from the Imperial court at Kyoto. The Imperial court, dominated by anti-foreign loyalists, was furious. Second, when his policy was opposed by senior Tokugawa kinsmen and the imperial loyalist movement, Ii responded with the Ansei Purge: between 1858 and 1859 over a hundred political opponents were executed, exiled, or stripped of office. Among the executed were the most prominent imperial loyalists of the period, including Yoshida Shōin.

The Ansei Purge made Ii the most hated political figure in Japan, particularly among the lower-ranking samurai of the Mito, Satsuma, and Chōshū domains. The Mito connection was personal: many of the executed loyalists were Mito retainers, and the Mito daimyō Tokugawa Nariaki had been forced into house arrest. Avenging them became the explicit motivation of the assassins.

The Plan

The Sakuradamon attack was conceived in the autumn of 1859 by a small group of Mito and Satsuma ronin meeting in secret in Edo. The plan called for an ambush during one of Ii's regular processions to Edo Castle. The location chosen was outside the main Sakurada Gate, at a point where the procession had to slow to enter. The number of attackers — eighteen — was deliberately small enough to maintain operational security and large enough to overwhelm Ii's bodyguard.

The morning of March 24th, 1860 was a tactically convenient one. Heavy snow had fallen the night before. The streets were unusually quiet. Ii's bodyguard, expecting a routine procession, were carrying their swords still in their saya (scabbards) and most had their hands warmed inside their kimono sleeves rather than on their hilts. The assassins took up positions along the route an hour before the procession arrived. Each was assigned a specific role: one to fire the signal pistol, one to attack the lead guards, others to hold the flanks, two to make the actual killing.

The Attack

When Ii's procession reached the appointed point at approximately nine in the morning, the lead assassin fired a Smith & Wesson pistol — almost certainly the first time a firearm had been used in a samurai assassination — into the front of Ii's palanquin. The shot wounded Ii but did not kill him. The other assassins closed with swords. Ii's bodyguards, hands stiff in the cold and weapons unprepared, were overrun in approximately four minutes. Two assassins reached the palanquin, dragged Ii out, and beheaded him. They took his head as evidence and fled in different directions.

Of the eighteen attackers, eight died at the scene from injuries inflicted by the bodyguard. Eight more were captured in the following weeks and executed. Two escaped briefly — one died of his wounds within months, the other surrendered the following year. The rest of the bodyguard, having lost their lord under conditions that made every man's failure visible, committed seppuku within days.

The Political Consequence

The bakufu's official response was paralysis. Ii's assassination had been carried out within five hundred meters of the seat of central government, by a small private group of ronin, against the most senior policy-making official. No previous Tokugawa-era political crisis had produced anything comparable. The bakufu could not claim it controlled its own city, let alone the country. It also could not punish the responsible domains — Mito and Satsuma — without escalating an already-dangerous political crisis.

Within months, the bakufu was in retreat on every major policy front. The Harris Treaty enforcement was effectively suspended. The Ansei Purge prisoners who survived were quietly released. The next senior bakufu official, Andō Nobumasa, had to operate as if his predecessor's policies had not existed. Andō himself was attacked in early 1862 (the Sakashitamon Incident) and survived only because his guards had learned from Sakuradamon what to expect. By 1863 the bakufu's credibility as a national authority was visibly broken. By 1867 it was over.

How He Was Remembered

Pre-war Imperial loyalist historiography treated Ii Naosuke as a near-traitor for signing the unequal treaty without Imperial sanction and as a tyrant for the Ansei Purge. Postwar Japanese scholarship has been more sympathetic. The treaty signing is now widely seen as the only realistic response to the gunboat threat — there was no military path to resistance, and delaying acceptance would have meant accepting harsher terms. The Ansei Purge has been re-evaluated as a desperate attempt to preserve a bakufu that was in fact too far gone to save.

The assassination itself remains the conventional turning point of Bakumatsu politics. Most modern Japanese historians date the bakufu's loss of operational credibility from March 24th, 1860. In the seven years between Sakuradamon and the Taisei Hōkan of 1867, the bakufu never recovered an initiative it had not had to defend. Whatever Ii's personal flaws, the office he held could not survive his death.

"If we wait for Imperial sanction we will wait until the foreign warships sit in the harbor of Kyoto."