For Japanese history the Emperor is as old as time. With changing times the power and role of the Emperor also changed.
Sources:
Peter Wetzler - Hirohito and War
Noriko Kawamura - Emperor Hirohito and the Pacific War
Noriko Kawamura - Emperor Hirohito and Japan's Decision to Go to War with the United States: Reexamined
Ikuhiko Hata - Hirohito: The Shōwa Emperor in War and Peace
Stephen Large - Emperor Hirohito and Showa Japan
藤原彰 - 徹底検証・昭和天皇 「独白錄」
