commander-in-chief; generalissimo
A supreme military rank or title, historically used for the highest commander of an army or state forces. In modern contexts, it may refer to the ceremonial title held by the Emperor of Japan under the former constitution.
The generalissimo took command of the entire army.
旧憲法下では、天皇は大元帥として陸海軍を統帥した。
Under the former constitution, the Emperor, as commander-in-chief, held supreme command of the army and navy.