 While still studying at Peabody, Dirksen became assistant organist to Paul Callaway at the Washington National Cathedral in February, 1942.Later that year, he began three-and-a-half years of military service during World War II, resuming his post at the cathedral in December, 1945.In 1949, Dirksen was also appointed director of the glee club at the cathedral's affiliated St. Albans School.