* 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.

* 1939 – Kate O ' Mara, English actress

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.

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.