Yamato didn't sink in 1937 but 1945. America wasn't in the war yet...the war had barely started! The Yamato was ordered and keel laid in 1937. Some claim WWII was the result of an arms race over battleships. While some countries could build ships with large guns, most were restricted and eventually resisted. Japan and Germany both felt overly restricted and went against the ban against large gun battleships.
I would call Hiroshima a major point. It's not a terminus for the main line. Nagoya is a terminus for JR Tokai, Osaka is one for JR West, and Okayama is one for JR Shikoku. I don't know much about Kyushu but I assume Fukuoka or Kitakyushu are terminus where you change train companies.
I consider a hub a central location for a major entity, core traffic point and operations facilities.