During the war, Steinbeck accompanied the commando raids of Douglas Fairbanks, Jr.'s Beach Jumpers program, which launched small-unit diversion operations against German-held islands in the Mediterranean.
Under krigen fulgte Steinbeck med på kommandomissioner under Douglas Fairbanks Jr.'s Beach Jumpers-program, hvor små afledningsoperationer blev igangsat mod tyskbesatte øer i Middelhavet.