The Oppositionists fought battles as they retreated North from Edo (Tokyo). One of the Opposition units was lead by Shinsengumi commander Hijikata Toshizo. They marched under a great white banner emblazoned with the Chinese characters Tosho Daigongen, an alternate name for the Toshogu Shrine of Tokugawa Ieyasu.
Hijikata's Tosho Daigongen unit fought and captured Utsunomiya Castle but were driven from the castle in a major offensive by Imperial forces. Hijikata and his Army of Toshogu eventually were defeated on the northern island of Ezo (Hokkaido).
Hopefully this will give those visiting Nikko more feeling of the historical significance of the Toshogu Shrine rather then just thinking of Nikko as another Japanese tourist destination full of temples and shrines.
Statue of Shinsengumi Commander Hijikata Toshizo