The guns of the Kaiyō Maru were still smoking when the news arrived from the road to Kyoto: the army was in full retreat.

It was the morning of January 28, 1868 — one day after the first shots of the Boshin War (Bōshin Sensō) cracked open the evening on the Toba road. While shogunate forces were stumbling back in disorder from Toba-Fushimi, their navy was winning Japan's first modern naval engagement fifty miles away in Awa Bay.

The sequence of events had its own dark comedy. Satsuma ships had gathered at Hyōgo harbor to transport troops back to Kagoshima after the fighting at Kyoto. Enomoto Takeaki — vice admiral of the Tokugawa navy, a man who had spent years studying in the Netherlands specifically to build and command exactly this kind of modern fighting force — saw the Satsuma squadron and moved to intercept. His flagship, the Kaiyō Maru, was the shogunate's most powerful warship: a steam-powered frigate he had personally overseen the acquisition of, the masterwork of his naval career.

In Awa Bay, off the coast of Awaji Island, the Kaiyō Maru closed on the Satsuma warship Kasuga. At ranges between 1,200 and 2,500 meters — the outer edge of effective gunnery for 1868 — both ships opened fire. The exchange was loud, smoky, and largely ineffective. Forty-three combined shots were fired. Neither ship was seriously damaged. Early modern naval gunnery on the open sea was brutally imprecise: the guns existed, the training was new, the rolling of the hull made accuracy a matter of luck as much as skill.

What decided the battle was not marksmanship but reinforcements. As additional shogunate vessels arrived — the Banryū and the Shōkaku — the tactical balance shifted. The Kasuga, faster than the Kaiyō Maru, broke off and fled south toward Kagoshima. A slower Satsuma transport, the Shōō, could not follow. Her crew, facing capture, ran her aground at Yukinoura and set her ablaze. The act was consistent with the samurai ethic that still pervaded even these new steam-powered ships: better to destroy what you cannot keep than allow it to be taken by the enemy.

The shogunate navy had won. Tactically, unambiguously, the Kaiyō Maru had driven off the enemy, sunk an enemy vessel, and controlled the waters off Osaka Bay. Enomoto had done exactly what he was built to do.

Aboard the Kasuga, in the chaos of incoming fire and the maneuvers of a ship turning hard to flee, a nineteen-year-old Satsuma gunner had steadied himself at his post and done his job. His name was Tōgō Heihachirō. He had already been under fire before: at fifteen, he had manned a coastal cannon during the Royal Navy's bombardment of Kagoshima in 1863, one of the strangest afternoons in the history of Anglo-Japanese relations. Awa was his second engagement. He survived it without particular notice and went home to Kagoshima.

Thirty-seven years later, in May 1905, Admiral Tōgō Heihachirō stood on the bridge of the battleship Mikasa in the Tsushima Strait (Tsushima kaikyō) and destroyed the Russian Baltic Fleet in a single afternoon. It was, and remains, the most decisive naval victory of the modern era. Japan, in the eyes of the world, had arrived as a great power. The teenage gunner who had fled from Enomoto's guns at Awa Bay had become the man the world called "the Nelson of the East."

But that was the future. On January 28, 1868, the Tokugawa navy's finest hour was also its last meaningful one. Two days later, Yoshinobu fled Osaka Castle in the night. The land war was over. Enomoto, refusing to surrender his fleet, took the Kaiyō Maru and the remaining shogunate warships north — far north, past the main island of Honshū, to the northern frontier of Ezo, the island now called Hokkaido. He established a short-lived republic there, the Republic of Ezo (Ezo Kyōwakoku), and held out for five more months after the rest of Japan had surrendered.

In November 1868, the Kaiyō Maru — the ship Enomoto had built his career around, the masterwork of a man who had devoted himself to giving Japan a modern navy — ran into a storm off Hokkaido and sank. Not by imperial cannon. By weather.

Enomoto was eventually captured, imprisoned, and then pardoned. The new Meiji government, impressed by his obvious competence and by the fact that he had offered to return sensitive naval codebooks rather than destroy them, absorbed him into the new order. He served as Japan's Navy Minister. He negotiated a territorial treaty with Russia. The admiral who had won the Tokugawa's last naval victory became a minister of the government that had defeated him.

The irony is the story of the entire Meiji transition: old loyalties, old skills, new uses.