What was Franklin Roosevelt’s rank during World War I? July 14, 2020 by Pamela Landy During World War I (1917-18), Franklin Roosevelt was the assistant secretary of the Navy. Related Answers Why do soldiers wear khaki? Has the U.S national debt ever been fully paid off? How large was the first national debt in the U.S.? How much money was raised from war bonds during World War II? What military ranks did James Stewart and Clark Gable reach during World War II? Why wasn’t Gregory Peck in uniform during World War II?