From Samurai Revolution: The Dawn of Modern Japan Seen Through the Eyes of the Shogun’s Last Samurai, by Romulus Hillsborough (Tuttle, 2014), Kindle pp. 374-377:
By the beginning of the Sixth Month, the Bakufu and its allies surrounded Chōshū on four fronts—Hiroshima to the east, Iwami to the northeast, Kyūshū (at Kokura across the Shimonoseki Strait) to the southwest, and on the Kaminoseki front (coming from Shikoku) in southeastern Chōshū. The so-called War on Four Fronts broke out on the Kaminoseki front on 6/7, when Bakufu naval forces took the island of Ōshima, which belonged to Chōshū.
Takasugi Shinsaku, in command of the Chōshū navy, lived up to his reputation for impetuousness. But first he took a short reprieve. On the way to Ōshima from Shimonoseki on the Heiin Maru—one of five ships in the Chōshū fleet—he stopped at Mitajiri and went directly to the home of a wealthy merchant named Sadanaga. He barged in on Sadanaga and informed him that he would “borrow a second-story room for just a short while.” He went up the ladder staircase—then suddenly all was quiet. After a while the merchant, wondering what had happened, went upstairs to find Takasugi asleep on the floor, his head cradled in his hands, his feet propped up against a wooden post. Sadanaga quietly descended the staircase to go about his business. Presently, he heard footsteps coming down the stairs. Takasugi appeared. He thanked the merchant, and said, “I’ll be back,” before hurrying back to his ship.
From Mitajiri Takasugi sailed directly to Ōshima, where he confronted four enemy ships—the bark Asahi, and three steamers: the Shōkaku [later the name of an aircraft carrier], the Yagumo [later the name of a cruiser], and the formidable 1,000-ton Fujisan—all much larger than the Heiin. Under the cover of night he maneuvered the 94-ton Heiin between the enemy ships to launch a surprise attack, in what one biographer calls “the first modern sea battle” in Japanese history. After two nights and one day of fighting, Chōshū retook the island on 6/16, forcing the enemy to retreat.
Meanwhile, fighting broke on the Hiroshima and Iwami fronts. The Chōshū forces at Hiroshima were commanded by Inoué Monta and Kawasé Yasushirō, the latter having commanded the Yūgekitai to fight alongside Takasugi in the rebellion at Shimonoseki. They easily defeated troops of Hikoné and Takada, which had been joined by troops under the Bakufu’s commissioner of the army, Takénaka Shigékata. The Chōshū forces penetrated into the Hiroshima domain, where they were confronted by troops of the Bakufu and Kii. Both sides were armed with modern rifles and artillery, the Bakufu having been equipped by the French. The fighting continued into the Eighth Month, when troops of Hiroshima, inclined toward Chōshū, cut their way between the two sides to force a stalemate. On the Iwami front, Chōshū fighters commanded by Murata Zōroku easily pushed into Hamada. Consequently, on 7/18, Matsudaira Ukonshōgen, daimyo of Hamada, a Tokugawa-related house, burned his castle and fled northeast to Matsué, also ruled by the Matsudaira.
The fiercest fighting took place on the vital southwestern front. Takasugi took command with the objective of capturing Kokura Castle. But his troops were too few—just one thousand Chōshū fighters faced twenty thousand Bakufu troops, including troops of Kokura, Kumamoto, and Kurumé, led by Ogasawara Nagamichi, who intended to cross the strait to invade Chōshū. Takasugi Shinsaku launched the first attack across the strait at dawn on 6/17. Ryōma reported to his family that Takasugi fired up the martial spirit of his fighters with “numerous casks of saké.” Takasugi attacked again on 7/3 and 7/27.
On 6/16, the day before the fighting broke out, Ryōma, with men from his Kaméyama Company, arrived at Shimonoseki on the warship Sakurajima Maru (aka the Union). “I led a Chōshū warship in battle,” he wrote to his family on 12/4. “I had no worries at all about fighting. It was truly amusing.” His amusement notwithstanding, Ryōma was not completely truthful in his devil-may-care attitude. “I was afraid that the Tokugawa navy would cut us off,” he confided in a letter to Miyoshi Shinzō on 8/16. Perhaps his greatest fear during the fighting was that Katsu Kaishū, recalled to his former post, might lead the Tokugawa fleet against Chōshū. “I could never fight against him,” he told Tosa’s minister of justice, Sasaki Sanshirō, in the following year.
Had Kaishū taken part in the fighting, the outcome may well have been different. Deploring the war, he submitted a letter to the Bakufu on 7/19 explaining how he could end the fighting in a matter of days “through leniency and harshness.” He would need to take command of “two or three warships … to attack [Chōshū’s] strategic points.” Then he would lead “two or three companies and hit them hard. Once we are victorious in one battle, I will … calmly solicit the advice of the feudal lords….” But Kaishū did not fight against Chōshū.
Chōshū was clearly winning the war. Senior Councilor Honjō Munéhidé, vice commander of the Bakufu forces on the Hiroshima front, wrote to the senior councilors in Ōsaka that the feudal lords had neglected orders to deploy sufficient numbers of troops, and that the majority of those deployed were peasants. There were shortages of rice and gold. And while the Chōshū troops, including the peasants, were armed with modern rifles, most of the Bakufu side depended on old-fashioned muskets.