He was born in the castle town of Hagi, the third son of Inoue Katsuyuki, a samurai of the Chōshū domain. His childhood name was Uhachi. His mother died while Uhachi was still a baby. His father was an enlightened man who valued Western learning, and he strongly influenced Uhachi's later path toward studying Western technology.
He was adopted as heir of Nomura Sakubei and changed his name to Nomura Yakichi. He studied at the domain school Meirinkan and, following his father who valued Dutch learning, set his sights on mastering Western knowledge. Until he later returned to his birth family, he was known in his youth as Nomura Yakichi.
After the arrival of the Black Ships, the Chōshū domain was ordered to guard the coast of Sagami. Yakichi went with his father, who was sent on guard duty, to Miyata in Sagami, and there he met and befriended Itō Hirobumi of the same domain. This meeting led to the bond by which the two later went to Britain together and supported the building of Meiji Japan.
On the domain's orders he studied in Nagasaki and, with Itō Hirobumi, learned Western military science at the Nagasaki Naval Training Center, but this did not satisfy him. He went on to study mainly navigation at the Bansho Shirabesho in Edo, then crossed to Hakodate seeking to learn navigation and English at Takeda Ayasaburō's school, studying in place after place.
He was made captain of a Western-style ship the domain had bought, but sensing the limits of his own seamanship, he longed all the more to study abroad. With Itō Hirobumi, Inoue Kaoru, Yamao Yōzō and Endō Kinsuke he secretly left Japan for Britain. These five were later called the Chōshū Five. In London he entered university and studied mining and railway technology.
Itō and Inoue Kaoru went home after about a year, and Yakichi and Yamao, who stayed on, lived in hardship as their funds ran low. Still they endured, and that year he graduated from the university in London. Answering Kido Takayoshi's repeated requests, he returned to Japan, rejoined his birth family, took back the surname Inoue and, taking a character from his father's name, called himself Inoue Masaru.
Answering Kido Takayoshi's call, he entered the new government and was appointed head of the mint and to a post over mines. As a subordinate of Itō Hirobumi, who had joined the government earlier, he worked on modernization and, with Itō, Ōkuma Shigenobu and others, came to push forward plans to build railways.
Under the British engineer Morel he learned the practical work of railway building and took on persuading people and politicians who opposed railways. When Morel died partway through construction, he worked to carry on the project in his place. That year Japan's first railway opened between Shinbashi and Yokohama. He had been appointed head of railways the year before.
He became director of the railway bureau and set up a training school for engineers inside Osaka Station. Until then Japan's railways had relied on foreign engineers, but many Japanese engineers emerged from this school. Masaru gradually reduced the number of foreign engineers and shifted to a system in which Japanese built the railways themselves.
On the railway linking Kyoto and Ōtsu, he placed engineers trained at the school on site, and he himself is said to have put on straw sandals, directed the work and swung a pickaxe. The work was difficult and an accident claimed lives, but that year the Ōsakayama Tunnel was completed. It was the first tunnel built by Japanese hands alone.
The line linking Tokyo and Kyoto was at first planned along the Nakasendō, but Masaru surveyed the ground himself, saw how hard construction would be, and decided to switch the route to the Tōkaidō. Pressing on despite struggles with the Hakone pass and bridging great rivers, he saw the Tōkaidō Line open along its full length that year. He received a decoration for this achievement.
As first head of the Railway Agency he also worked hard for the full opening of the Tōhoku Main Line, and that year Tokyo and Aomori were linked by rail. The same year, with Ono Gishin and Iwasaki Yanosuke, he founded Koiwai Farm in Iwate. He later called it atonement for destroying fine farmland by laying railways, but the farm struggled with the harsh climate and kept running at a loss.
Even after retiring as head of the Railway Agency three years earlier, he kept seeking ways to develop railways. That year he founded a locomotive-building company in Osaka, aiming to make locomotives in Japan rather than buy them from abroad. He later also served as president of a railway association, devoting his life to railways.
He traveled to Europe to inspect railways and other matters, surveyed various places centered on Britain and returned to London, but a chronic kidney illness worsened and he died there in London. It was the end of his life in the place where he had studied in his youth. His remains were cremated, brought back to Japan and buried at Tōkai-ji in Shinagawa, Tokyo.
Kido TakayoshiInoue KaoruŌkuma ShigenobuItō Hirobumi
Itō HirobumiTanaka ShōzōŌyama IwaoNiijima JōSaigō TsugumichiMutsu MunemitsuInoue KowashiNiijima Yae
People of the Meiji period ・ People by period
Based on facts found in textbooks and biographies. Uncertain points are marked as such.