会津戦争
Ōyama's first wife Sawa died of puerperal disorder. Second wife Sutematsu (a survivor of the Battle of Aizu, a sister of former Aizu retainers Yamakawa Hiroshi and Yamakawa Kenjirō) was one of the first female students sent to the United States as part of the Iwakura Mission in the early 1870s. She spent eleven years there, graduating from Vassar College in 1882. In the next year she accepted her former enemy's proposal.