largest city, Yamaguchi ken (prefecture), Honshu, Japan, occupying a strategic position on the Shimonoseki-kaikyō (Shimonoseki Strait) between Honshu and Kyushu. The city was formerly called Akamaga-seki and Bakan. Its modern development began in 1905 with the opening of railroad ferry service to Moji (now Kita-Kyūshū), Kyushu; later links include a railroad tunnel (1942) and a vehicular-pedestrian tunnel (1958) under the strait. An international ferry service opened between Shimonoseki and the port of Pusan, South Korea, in 1970. Shimonoseki became a heavy-industrial centre after 1942, and in 1940 its port was amalgamated with those of Moji and Kokura into the single port of Kammon. During the 1970s the Shinkansen (“New Trunk Line”) railway service linking Tokyo with Ōsaka was extended to Shimonoseki, en route to northern Kyushu through an underground tunnel beneath the Shimonoseki Strait.