Taisho Period Taisho Emperor Japanese Boy Scouts being trained with rifles. The Taishō period (大正時代, Taishō jidai?, "period of great righteousness"), or Taishō era, is a period in the history of Japan dating from July 30, 1912 to December 25, 1926, coinciding with the reign of the Taishō Emperor. The health of the new emperor was weak, which prompted the shift in political power..