Defense Secretary Dr. Mark T. Esper swears-in retired Navy Rear Adm. Kenneth Braithwaite to serve as the next Secretary of the Navy, in Washington, D.C., May 29. - Defense Secretary Dr. Mark T. Esper swears-in retired Navy Rear Adm. Kenneth Braithwaite to serve as the next Secretary of the Navy, in Washington, D.C., May 29.