Katsu Kaishū
A native of Aizu, Yamamoto claimed descent from the famed military strategist Yamamoto Kansuke. A child prodigy, he could read at age four, and recite Chinese "Jueju" poetry at age five. He was sent to Edo at age 22, to study with Katsu Kaishū, under the direction of Sakuma Shōzan, "rangaku" and modern military science. He returned to Aizu at age 28, and became an instructor of hōjutsu at the Nisshinkan, the Aizu domain's academy.