A moderate who attempted to restrain the rise of militarism, Okada was among those targeted by a group of rebel officers in the February 26 incident of 1936.

As a senior statesman during the Pacific War, Okada was a central figure in efforts to oust Prime Minister Hideki Tojo and seek peace with the allies.

Promoted to rear admiral on 1 December 1913, Okada served in a number of desk jobs thereafter, including that of the Naval Shipbuilding Command.

In 1927, he became Minister of Navy in the administration of Tanaka Giichi, but resigned in 1929 to assume the post of military councillor on the Supreme War Council.

Okada was one of the democratic and moderate voices against the increasing strength of the militarists, and was therefore a major target for extremist forces pushing for a more totalitarian Japan.

He narrowly escaped assassination in the February 26 Incident of 1936, largely because rebel troops killed Colonel Denzō Matsuo, brother-in-law as well as personal secretary of Okada's, by misidentifying him as the prime minister.

During World War II, Okada formed a group of like-minded politicians and military officers seeking an early end to the hostilities.