Yamamoto was born in Kagoshima in Satsuma Province (now Kagoshima Prefecture) as the son of samurai who served the Shimazu clan. As a youth, he took part in the Anglo-Satsuma War. He later joined Satsuma's Eighth Rifle Troop; in the Boshin War that ended the Tokugawa shogunate, fighting at the Battle of Toba-Fushimi and other locations; he was also aboard one of the ships that pursued Enomoto Takeaki and the remnants of the Tokugawa fleet to Hokkaidō in 1869.
Yamamoto was born in Kagoshima in Satsuma Province (now Kagoshima Prefecture) as the son of samurai who served the Shimazu clan. As a youth, he took part in the Anglo-Satsuma War. He later joined Satsuma's Eighth Rifle Troop; in the Boshin War that ended the Tokugawa shogunate, fighting at the Battle of Toba-Fushimi and other locations; he was also aboard one of the ships that pursued Enomoto Takeaki and the remnants of the Tokugawa fleet to Hokkaidō in 1869.