[5] Completing his Battle Force tour in March 1938,[4] he transferred to the destroyer USS Claxton (DD-140),[4][6] patrolling off Spain in defense of American interests during the Spanish Civil War.

[7] In January 1940,[4] Semmes reported for duty aboard the new aircraft carrier USS Wasp (CV-7),[8] then fitting out at the Fore River Shipyard in Quincy, Massachusetts,[9] and he became a member of her first crew when she was commissioned on 25 April 1940.

With Semmes still aboard, Wasp patrolled in the West Indies early in 1942, then deployed to Scapa Flow in the Orkney Islands in March 1942 to support the British Home Fleet in covering Arctic convoys bound for the Soviet Union.

[11] Semmes went over the side[11] and at one point saw an 8-foot (2.4 m) shark circling his group of survivors as they swam toward the destroyer USS Duncan (DD-485) for rescue but decided not to tell the other men he had seen it.

[9] In December 1942, Semmes reported to the new destroyer USS Sigsbee (DD-502),[4] then fitting out at the Federal Shipbuilding and Dry Dock Company in Kearny, New Jersey.

PICKING (DD-685), in action against the enemy on 18 May 1945, during the assault and occupation of Okinawa...Gallantly responding to the need for assistance by a friendly destroyer grounded on a reef within one mile of the hostile coast, Commander Semmes skillfully maneuvered his ship through the hazardous, obstructed waters in a determined attempt to re-float the stricken vessel.

Again closing the helpless vessel, he daringly stood by, continuing his fierce and relentless bombardment of opposing shore emplacements and rendering heroic service in the rescue of personnel...[1]Semmes also received the Bronze Star Medal with Combat "V" for heroism in command of Picking.

[22][26] From 1955 to 1957, Semmes was chief of staff to the Commander, Destroyer Force, Atlantic Fleet, based at Newport, Rhode Island,[22][26] followed by a year of study at the National War College in Washington, D.C., from which he graduated in 1958.

[22] On 18 July 1958,[4] during his tour aboard Shenandoah,[26] President Dwight Eisenhower approved his promotion to rear admiral,[4] making him the first member of his Naval Academy graduating class to be selected for flag rank.

[4][28] After a tour ashore as Assistant Chief of Naval Personnel for Plans,[26] Semmes served as Commander, Middle East Force, in the Persian Gulf from 30 May 1962 to 9 July 1963.

[4][26] Semmes was promoted to vice admiral on 1 April 1964,[4][30] and he became Chief of Naval Personnel the same day,[4] serving in the position until March 1968; he was awarded the Distinguished Service Medal and the Legion of Merit for the tour.

During this crucial period of an accelerating tempo of operations incident to the conflict in Southeast Asia, Vice Admiral Semmes has demonstrated dynamic leadership, outstanding executive ability and exceptional foresight in anticipating and solving the diverse personnel problems associated with rapidly expanding manpower requirements.

His deep concern for their morale and welfare has been manifested in programs he has vigorously sponsored to increase compensation eligibility, educational opportunity, and career attractiveness.

Major improvements in planning and management techniques to provide more effective personnel utilization have clearly demonstrated Vice Admiral Semmes' ingenuity and flair for innovation.

Vice Admiral Semmes provided the blueprint for many of the Navy's most critical programs of the future including LAMPS, Anti-Ship Missile Defense, and the new PF Class ship [later the Oliver Hazard Perry-class frigate].