Emperor vs Shogun in Boshin War, 1868-'69 戊辰戦争
Boshin Civil War was marked as the restoration of Imperial reign after seven centuries’ Samurai governance, followed by Japan's revolutionary changes and reforms during the Meiji period of 1868-1912 (明治維新).
(My not-too-distant ancestor fought on pro-Shogunate side and lost his life with a wife and two infants left)