During the Edo Period, the Saga Clan had six small boat dock sites within its domain for the maintenance of its Japanese-style boats. One of these was located at Mietsu.
In 1855, the Saga Clan sent many of its samurai to the Nagasaki Naval Training Institute established by the shogunate to learn about naval navigation and shipbuilding skills.
And then, in 1858, the clan built the Ofunate-Keikosho Naval Academy in Mietsu at the site where the small boat docks had been for the purpose of spreading the knowledge and skills acquired at the Nagasaki Naval Training Institute to others within the clan. This is how the Mietsu Naval Dock came into existence.
The area is now the Sano Memorial Park, comprised of the Tsunetami Sano Memorial Museum and a History Park.
During the Edo Period, the Saga Clan took turns with the Fukuoka Clan to patrol the port of Nagasaki under the orders of the shogunate.
In 1808, the HMS Phaeton incident occurred while the Saga Clan was in charge of upholding the security of the port.
The British frigate Phaeton entered the port of Nagasaki by pretending to be a Dutch ship, and demanded firewood and food after taking Dutch trade representatives as hostages. Nagasaki’s magistrate office and the Saga Clan had no choice but to comply with these demands, as they lacked the military power to fight off the foreign ships. The shogunate’s magistrate in Nagasaki at the time, MATSUDAIRA Yasuhide, took responsibility for this incident by committing seppuku (suicide by disembowelment), and the head of the Saga Clan, NABESHIMA Narinao, was placed under house arrest. After this incident, the Saga Clan began to look upon Europe and the Americas as a threat.
The Opium War started in 1840 between the Qing Dynasty (current-day China) and Great Britain, with the British forces coming out victorious due to their dominant military power. The defeat of the Qing Dynasty, which was considered by the Japanese to be a mighty nation at the time, made the Saga Clan feel an increased sense of danger from the threat of European and American nations invading Asia, and thus, proceeded to develop a Western-style navy and maintain Western-style ships in order to acquire the strength to meet these foreign forces.
After the Nagasaki Naval Training Institute closed in 1859, the Saga Clan started its own unique naval training, and the functions of the Ofunate-Keikosho Naval Academy were expanded so that it could serve as a naval facility. By 1861, the site had a production area to create the parts needed to repair Western-style ships, as well as a dry dock to pull in boats for repair. Mietsu Naval Dock had evolved into a site that served to provide naval education, ship navigation and shooting training, and also acted as a facility for repair and shipbuilding, using the Western-style ships owned by the Saga Clan at the end of the Edo Period.
Japan’s first steamboat, the Ryōfūmaru, was built here in 1865.
The Saga Clan had been actively learning, studying, and implementing Western technology, even before they built Mietsu Naval Dock. The Tsuiji Reverberator Furnace site, the Seirenkata Institute site, and the Tafuse Reverberator Furnace site were all deeply connected to Mietsu Naval Dock, and are sites of industrial heritage that show that the Saga Clan had been making efforts to make use of modern scientific technology during the late Edo Period.