Answer
Yonai Mitsumasa was the predecessor of Yamamoto Isoroku as Commander-in-Chief of the Combined Fleet. Yonai was appointed to the position on July 31, 1939, and served until April 18, 1941, when he was replaced by Yamamoto. Yonai was a moderate who opposed Japan's entry into World War II, and he resigned from his position as Commander-in-Chief of the Combined Fleet in protest of Japan's decision to go to war.