This LIFE photo from April 1945 shows the last surviving head of state who served in uniform during World War II.

At the age of 19, Queen Elizabeth II (service number 230873) joined the Auxiliary Territorial Service (ATS) in February 1945.  She was recruited as a an honorary Second Subaltern, becoming a trained mechanic and truck driver, and promoted to honorary Junior Commander 5 months later.

Fun Fact: Winston Churchill's youngest daughter Mary was also a member of the ATS.