미토 번
In 1852, Katsura went to Edo (present-day Tokyo) to study swordsmanship, established ties with radical "samurai" from the Mito Domain (present-day Mito, Ibaraki Prefecture), learned artillery techniques with Egawa Tarōzaemon, and (after observing the construction of foreign ships in Nagasaki and Shimoda), returned to Chōshū to supervise the construction of the domain's first western-style warship.