 World War II engulfed the United States before "Markab" steamed into Ensenada Honda, Puerto Rico, her first port of call.The new wartime demands on the Navy caused this voyage to terminate at Mobile, Alabama on 8 January 1942 where she was converted to a destroyer tender.Sixteen days later she was redesignated AD-21, but it was 27 September before Commander Brown again commanded a fully commissioned vessel.