When deciding whether to accept the Potsdam Declaration and surrender at the end of World War II, even the Prime Minister was not allowed to decide it by himself and so they had to ask the Emperor to make an 'Imperial decision'.
また、終戦の際、ポツダム宣言の受諾・降伏を決定することは総理大臣にも出来ず、天皇の「聖断」を仰ぐ他なかった。