On the conclusion of the war, Satō's talents and heroism were awarded with an assignment to the staff of Admiral Yamamoto Gonnohyōe within the Navy Ministry's Naval Affairs Department.

Upon his return to Japan, he published On the Defense of the Empire while an instructor at the Naval War College, which advocated the Navy as the main force of national security and military strength.

During the Russo-Japanese War, Satō served as a staff officer of the IJN 2nd Fleet under Vice Admiral Kamimura Hikonojō, partly to protect him from political retaliation by the Imperial Japanese Army, who were incensed by his thesis that the navy was of more importance.

He also began urging the Japanese government to maintain at least a 70% capital ship level over the United States, Japan's hypothetical rival.

Named to the House of Peers in 1934, Satō was a major opponent to Japan's participation in the Washington Naval Treaty (and thus a member of the Fleet Faction following World War I until his death in 1942.)