The eleventh lord of Satsuma Domain, he had a deep interest in Dutch learning and Western science from childhood, and after becoming domain lord in 1851 actively promoted industrial development and national enrichment. He led the introduction of Western-style warships, cannon, firearms, textile manufacturing, glassmaking, and telegraph technology, and built Japan's first Western-style warship, the Shoheimaru. He was also a pioneering figure who made Japan's first attempts at gas lighting, telegraphy, and photography. He actively recruited Saigo Takamori, Okubo Toshimichi, and other future architects of the Restoration from among Satsuma retainers, nurturing their talents. Together with Matsudaira Shungaku, Yamauchi Yodo, and Date Munenari he was counted among the 'Four Wise Lords of the Bakumatsu.' In the shogunal succession dispute he backed Hitotsubashi Yoshinobu and clashed with Tairo Ii Naosuke. On July 16, 1858, he died suddenly at the age of forty-nine, only seven years into his rule as domain lord. The circumstances of his death are considered suspicious and some suspect poisoning. His death had a major impact on Satsuma's political direction and brought deep grief to Saigo and other loyalist figures. Sengan-en (Iso Garden, now in Kagoshima City), developed during his era, still draws many visitors as a celebrated scenic site.