In the first month of 1868 Tokugawa Yoshinobu, beaten at Toba and Fushimi, slipped out of Osaka Castle under cover of night and reached the sea off Shinagawa in the warship Kaiyō Maru. That was on the eleventh day of the first month. Oguri Kōzukenosuke Tadamasa's diary has this in the entry for the next day, the twelfth.
Went up to the castle, where it was said that, the army having been beaten, his lordship returned last night from Osaka to the sea off Shinagawa in the ship Kaiyō Maru … it is said that Osaka Castle was a great defeat and that he withdrew from it.
From that day a great council was held inside Edo Castle. What Oguri set out there was the plan of operations later known as the Hakone annihilation plan.
Bombardment from Suruga Bay
The essentials were simple: let the enemy into the mountains at Hakone, then cut off his line of retreat.
The shogunate's naval strength was then overwhelmingly superior: eight modern ships, headed by the Kaiyō Maru with her twenty-six guns. The fleet was to be sent round into Suruga Bay to bombard the massed columns of the western army as they came east along the Tōkaidō. The troops behind them would have nowhere to take cover. That is Sakamoto Fujiyoshi's summary of it.
In the fuller version that has come down, the plan has four stages.
Send the fleet round into Suruga Bay, bombard the massed columns of the western army on the Tōkaidō, and cut their supply line and their line of retreat
With the picked trained battalions, draw the enemy, cut off from supply and from reinforcement, east of Hakone, and crush them at a stroke
Send part of the navy round into the waters off Hyōgo to bombard them, cutting the western army's communication with its base of supply and isolating it
Meanwhile the disaffected in Kyushu would rise and strike at Satsuma where it was weak, and the lords great and small across the country, seeing how things stood, would come over to the shogunate's side
It was a design not only for pushing the enemy's main force into a defile but for cutting away the supply line itself from the sea. No one could have drawn it up without knowing where the road east along the Tōkaidō narrows and where it comes down to the water.
The imperial army was in fact stuck fast
That the plan was no fancy appears from the real state of the advancing side. The army that went east in high spirits behind the brocade banner, to the tune “Miya-san, Miya-san” that Shinagawa Yajirō had made, was fine on the surface but short of both rations and money. It was stuck fast as early as Ōtsu, and was stuck on the highway again and again before it reached Edo. It could not even pay its inn bills.
Each time, it was Mitsui that sent chests of a thousand ryō in haste. What could not be paid was to be repaid after the Restoration. It was by this that the brocade banner was able to advance at all, and the Mitsui storehouses were emptied to the point of selling off old gold and silver. That Mitsui obtained the privilege of handling the government's money and exchange once the revolution was accomplished followed as a matter of course. Oguri's idea of cutting the supply from the sea struck at this weakness.
“Our heads would not have been on our shoulders”
Murata Zōroku (Ōmura Masujirō), who planned the imperial army's operations, is said to have remarked when he heard of this plan later that, had it been carried out, their heads would not have been on their shoulders. It is said to have been at a gathering where the imperial army's staff officers and inspectors were talking after the fighting at Ueno.
The fifteenth day of the first month, in the Fuyō Room
Oguri's proposal was not accepted. To his mind Yoshinobu's conduct was far too inconsistent. If Satsuma were the evil at the sovereign's side, then removing it was the right course to the end. Chōshū had been called an enemy of the court and had fought on regardless, which was precisely why its position had now been reversed. Why submit merely because the first battle had gone against them? He must have thought so, Sakamoto Fujiyoshi writes.
Of this dismissal there is the story that Oguri caught the sleeve of Yoshinobu as he tried to withdraw to the inner rooms and would not let go, and that a pale Yoshinobu dismissed him with his own mouth, the only such dismissal in person by a shogun in the shogunate's history. Sakamoto, however, denies this plainly: it makes good drama, but it is not historical fact. What actually happened was on the fifteenth day of the first month, in the Fuyō Room, with the senior councillors in attendance, where Sakai Uta-no-kami declared it. Oguri's own diary records the day thus.
In the Fuyō Room Sakai Uta-no-kami declared that I was relieved of office and placed on ordinary attendance. Left after the seventh and a half hour of the evening … Sent notice of the above to my colleagues and to my relatives.
Told of his dismissal, he left after half past the seventh hour of the evening and sent word at once to his colleagues and his relatives. The entry is flat. Among former shogunal officials it was also said that Oguri was dismissed not for arguing to fight on but for the unprecedented discourtesy of catching the shogun's sleeve and speaking so violently.
What was it that saved Edo?
There is the criticism that “had Oguri's view been accepted, Edo would have become a field of fire”. It rests on the orthodoxy, held since the Meiji era, that Edo was saved by the meeting between Saigō and Katsu. Sakamoto Fujiyoshi rejects this as mistaken.
Saigō thought of nothing to the last but an attack on Edo, and had fixed the fifteenth day of the third month as the day of the general assault. Even after Yamaoka Tesshū met him at the risk of his life on the ninth day of the third month, he sent Kinashi Seiichirō to Yokohama on the thirteenth day of the third month to ask Parkes that, since the fifteenth was to be the general assault and there would be many wounded, he take charge of their relief. No one with no intention of fighting makes such a request.
Saigō gave up the attack because Parkes then warned him sternly on three grounds: that to attack while Yoshinobu was declaring his submission did not agree with the law of nations; that war would bear on the safety of the British residents at Yokohama; and that if fire reached Edo and Yokohama, Britain's losses in trade would be great. On hearing Kinashi's report, even Saigō is said to have changed colour. Keeping the matter strictly secret, he met Kaishū on the fourteenth and called off the attack on Edo in a way that left the credit to Kaishū.
Why, then, was Parkes opposed? Sakamoto gives, besides the blow to Anglo-Japanese trade, the fact that a strong French squadron was lying at Yokosuka at the time. The British squadron was far away, operating towards western Japan; if Edo and Yokohama became a battlefield Britain could not protect her residents, whereas France could. Yokosuka worked as unspoken pressure on Parkes — so that the Yokosuka ironworks, into which Oguri had poured himself, checked Saigō's use of force without anyone intending it.
The Hakone plan was never carried out. But the works Oguri left behind in trying to defend Edo from the sea played that part in another form.
Sources: Sakamoto Fujiyoshi, Oguri Kōzukenosuke no Shōgai (the life of Oguri Kōzukenosuke), Kōdansha, 1987; Tatsunami, the journal of the memorial society
→ The great council at Edo Castle