* 1939 – 1945, the Second Battle of the Atlantic.

Subsequent formalizations were framed as attempts to define " effective calculability " or " effective method "; those formalizations included the Gödel – Herbrand – Kleene recursive functions of 1930, 1934 and 1935, Alonzo Church's lambda calculus of 1936, Emil Post's " Formulation 1 " of 1936, and Alan Turing's Turing machines of 1936 – 7 and 1939.

* 1890 – Anthony Fokker, Dutch aviation engineer ( d. 1939 )

* 1939 – André Ouellet, French-Canadian politician

* 1852 – Ferdinand von Lindemann, German mathematician ( d. 1939 )

* 1939 – Alan Ayckbourn, English writer

* 1939 – Johnny Raper, Australian rugby league footballer

* 1939 – The 1939-40 New York World's Fair opens.

* 1939 – NBC inaugurates its regularly scheduled television service in New York City, broadcasting President Franklin D. Roosevelt's N. Y. World's Fair opening day ceremonial address.

* 1939 – First flight of the turbojet-powered Heinkel He 178, the world's first jet aircraft.

* 1939 – William Least Heat-Moon, American author

* 1939 – Edward Patten, American singer-songwriter and producer ( Gladys Knight & the Pips ) ( d. 2005 )

* 1939 – Bulle Ogier, French actress

* 1939 – Romano Prodi, Italian politician and statesman

* 1939 – Hércules Brito Ruas, Brazilian footballer

* 1939 – Albert Einstein and Leó Szilárd write a letter to Franklin D. Roosevelt, urging him to begin the Manhattan Project to develop a nuclear weapon.

* 1939 – Benjamin Barber, American theorist

* 1939 – Wes Craven, American director

* 1939 – John W. Snow, American politician, 73rd United States Secretary of the Treasury

* 1984 – Marvin Gaye, American singer ( The Moonglows ) ( b. 1939 )

* 2001 – Trinh Cong Son, Vietnamese composer ( b. 1939 )

Eastern European theorists include Pyotr Stolypin ( 1862 – 1911 ) and Alexander Chayanov ( 1888 – 1939 ) in Russia ; Adolph Wagner ( 1835 – 1917 ), and Karl Oldenberg in Germany, and Bolesław Limanowski ( 1835 – 1935 ) in Poland.

Kate O ' Mara ( born Frances M. Carroll, 10 August 1939, Leicester ) is an English film, stage and television actress.

Michael C. Ford ( born 1939 ), Kate Braverman ( born 1950 ), Eloise Klein Healy, Bill Mohr, Laurel Ann Bogen, met at Beyond Baroque

After finding an audience with Kate Smith's listeners, The Aldrich Family was launched in its own series as a summer replacement program for Jack Benny in NBC's Sunday night lineup, July 2, 1939, and it stayed there until October 1, 1939, when it moved to Tuesday nights at 8 p. m., sponsored by General Foods's popular gelatin dessert Jell-O, which also sponsored Jack Benny at the time.

* Kate Dickinson Sweetser (?- 1939 ), fiction author

Writing on Doctrine and Training in the German Army 1919 – 1939, O ’ Neill stated:

Early films, including those from the silent era, which feature the station include Traffic in Souls ( 1913 ), which starred Matt Moore ; The Yellow Passport ( 1916 ), starring Clara Kimball Young ; My Boy ( 1921 ), starring Jackie Coogan ; Frank Capra's The Strong Man ( 1926 ), starring Harry Langdon ; We Americans ( 1928 ), starring John Boles ; The Mating Call ( film ), 1928, co-starring Thomas Meighan and Renée Adorée ; Ellis Island ( 1936 ), starring Donald Cook ; Paddy O ' Day ( 1936 ), starring Jane Withers ; Gateway ( 1938 ), starring Don Ameche ; Exile Express ( 1939 ), which starred Anna Sten ; I, Jane Doe ( 1948 ), starring Ruth Hussey and Vera Ralston, and Gambling House ( 1951 ), starring Victor Mature

* 1939 – William O ' Connor, American fencer ( b. 1864 )

* 1939 – Gordon O ' Connor, Canadian politician

* 1864 – William O ' Connor, American fencer ( d. 1939 )

In 1939, Steiner was borrowed from Warner Bros. by David O Selznick to compose the score to Gone with the Wind.

* 1939 – Tom O ' Connor, British comedian

" O Canada " had served as a de facto national anthem since 1939, officially becoming Canada's national anthem in 1980 when the Act of Parliament making it so received Royal Assent and became effective on July 1 as part of that year's Dominion Day celebrations.

* 1939 – O. V. Wright, American soul singer ( d. 1980 )

Hollywood was in the midst of a widely publicized search to find an actress to portray Scarlett O ' Hara in David O. Selznick's production of Gone with the Wind ( 1939 ).

* March 2 – Darcy O ' Brien, American author ( b. 1939 )

In 1939, Lombard took roles opposite James Stewart in producer David O. Selznick's Made for Each Other ( 1939 ) and Cary Grant in In Name Only ( 1939 ).

* Tower of London ( 1939 ): Elizabeth was played by Barbara O ' Neil.

* One of the main characters in Eugene O ' Neill's play The Iceman Cometh ( 1939 ), Larry Slade is an ex-anarcho-syndicalist.

It was formed in Chicago in 1936 by Louis Skidmore and Nathaniel Owings ; in 1939 they were joined by John O. Merrill.

* Dusty Springfield ( 1939 – 1999 ), pop singer ( born Mary O ' Brien )

Shearer was also one of the many actresses considered for the role of Scarlett O ' Hara in Gone With The Wind ( 1939 ).

The films produced were not successful enough, and the company was saved from bankruptcy only when RKO Pictures offered Laughton the title role ( Quasimodo ) in The Hunchback of Notre Dame ( 1939 ), with Jamaica Inn co-star O ' Hara.

John L. Sullivan ( Joel McCrea ), a popular young Hollywood director fresh from a string of very profitable, but shallow comedies ( e. g. Ants in Your Plants of 1939 ), tells his studio boss, Mr. Lebrand ( Robert Warwick ), that he is dissatisfied and wants his next project to be a serious exploration of the plight of the downtrodden, to be based on the socially-conscious novel O Brother, Where Art Thou?

United States Supreme Court Associate Justice William O. Douglas was one famous summer visitor to Wallowa County, building a vacation cabin on Lostine River Road in 1939.

The competition to play Mammy in Gone with the Wind ( 1939 ) had been almost as stiff as that for Scarlett O ' Hara.