He was born in Shiba, Edo, the third son of the hatamoto Shitara Sadatomo. His mother was a daughter of Hayashi Jussai, head of the Hayashi house that oversaw shogunate learning, and his uncles included Torii Yōzō and Hayashi Fukusai. Raised in a family that prized learning, he was steeped in Chinese studies from childhood. As a third son, he had no prospect of inheriting.
He was adopted as son-in-law by the hatamoto Iwase Tadamasa and became heir to the Iwase house of 800 koku. This opened the way for him to serve the shogunate in office. Still without a post, he devoted himself to study and showed his talent to those around him. It was the first step toward his later role in diplomacy.
He passed the major examination at the shogunate's Shōheizaka academy and was rewarded for his excellent results. Later he headed the academy in Kōfu, and on returning to Edo he became a professor at the Shōheizaka academy. His deep Confucian learning later gave him logical strength in dealing with foreign powers.
The year after Perry's arrival, the senior councillor Abe Masahiro recognized his talent and promoted him to metsuke, an inspector of the shogunate. In charge of coastal defense, he worked hard to establish the military academy, the Bansho Shirabesho for studying Western books and the Nagasaki Naval Training Center, and to build the Shinagawa forts. He became one of the young reformers.
When the Russian envoy Putyatin arrived, he went to Shimoda to take part in negotiations and witnessed the conclusion of the Russo-Japanese Treaty of Amity. Facing a foreign envoy directly made him keenly aware of the need to learn about world affairs. He later asked to go to Hong Kong to study conditions firsthand, but this was not realized.
He negotiated more than a dozen times with the American consul general Harris and signed the Harris Treaty with Inoue Kiyonao. Admitting Japan had no experience of trade, he questioned each article in turn, reducing the ports to be opened and barring foreigners from traveling freely in the interior. Harris reportedly said that Iwase often out-argued him into changing articles.
Becoming commissioner of foreign affairs, he also attended and signed the commercial treaties with the Netherlands, Russia, Britain and France. Iwase was the only person involved in all five treaties, including the American one. The treaties retained disadvantages such as consular jurisdiction and the lack of tariff autonomy, which became later challenges.
When the shogunate decided to open a port at Yokohama village across the bay instead of Kanagawa as named in the treaty, he objected, valuing the treaty's wording. Because he had also backed Hitotsubashi Yoshinobu in the shogunal succession dispute, he was moved in the Ansei Purge under the tairō Ii Naosuke to a minor post overseeing buildings.
He was dismissed from office and ordered into confinement at home. At Kiun'en in Mukōjima, Edo, he led a quiet life enjoying calligraphy and painting. Though removed from the front line of diplomacy, his foresight was recognized by later generations, who even raised a monument to him as the first advocate of opening Yokohama.
Disheartened, he fell ill and died in his early forties. His active years as a diplomat lasted only about five, yet he was praised with Mizuno Tadanori and Oguri Tadamasa as one of the three great men of the late shogunate. In the Taishō era his achievements earned him a posthumous rank, and he appears in Shimazaki Tōson's novel Before the Dawn.
Matthew C. PerryTownsend HarrisOguri TadamasaShimazaki TōsonIi NaosukeAbe Masahiro
Ii NaosukeNabeshima Naomasa (Kansō)Yoshida TōyōShimazu HisamitsuAbe MasahiroKatsu KaishūŌmura MasujirōJohn Manjirō
People of the Edo period ・ People by period
Based on facts found in textbooks and biographies. Uncertain points are marked as such.