* 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 Lise Meitner and Otto Robert Frisch determine that nuclear fission is taking place in the Hahn-Strassmann experiments

Lise Thibault ( born April 2, 1939 ) is a Canadian civil servant who was appointed the 27th Lieutenant Governor of Quebec on January 30, 1997.

Spontaneous fission became popular soon after its discovery in 1940 by K. Petrzhak and G. Flerov owing to both military and peaceful applications of neutron-induced fission discovered in 1939 by Otto Hahn, Lise Meitner and Fritz Strassmann, employing the large amount of energy released during the process.

* 1939 – Roy Romanow, Canadian politician

* 1885 – Édouard Fabre, Canadian runner ( d. 1939 )

* 1939 – Red Berenson, Canadian ice hockey player

* 1939 – Francis Fox, Canadian politician, member of the Senate

* 1939 – Jean Beaudin, Canadian film director and screenwriter

* 1939 – Raôul Duguay, Canadian artist, poet, musician, and political activist

* John Ford Messer ( 1889 – 1949 ), Canadian local-level legislator ; served as Conservative member of New Brunswick Legislative Assembly from 1939 to 1944

* 1939 – Anne Heggtveit, Canadian alpine skier

* 1939 – J. C. Tremblay, Canadian ice hockey player ( d. 1994 )

* 1939 – Cesare Maniago, Canadian ice hockey player

* 1939 – Gordon O ' Connor, Canadian politician

* 1939 – Sidney Altman, Canadian biologist, Nobel laureate

* 1939 – The Canadian National War Memorial is unveiled by King George VI and Queen Elizabeth in Ottawa.

* 1939 – Bill Graham, Canadian politician

* 1939 – Margaret Atwood, Canadian poet, novelist, critic and essayist

* 1939 – Norman Bethune, Canadian doctor and humanitarian ( b. 1890 )

* 1861 – James Naismith, Canadian inventor of basketball ( d. 1939 )

* 1939 – Robin Spry, Canadian filmmaker and producer ( d. 2005 )

* 1939 – Len Cariou, Canadian actor

First lady Dolley Madison rescued a painting of George Washington, and in 1939, a Canadian man returned a jewelry box to President Franklin Delano Roosevelt, claiming that his grandfather had taken it from Washington.

His government also made the Canadian Broadcasting Corporation a crown corporation in 1936, created Trans-Canada Airlines ( the precursor to Air Canada ) in 1937, and formed the National Film Board of Canada in 1939.

In the lead-up to World War II in 1939, King affirmed Canadian autonomy by saying that the Canadian Parliament would make the final decision on the issue of going to war.

" Double Vision: Ernest Lapointe, Mackenzie King and the Quebec Voice in Canadian Foreign Policy, 1935-1939 ," Journal of Canadian Studies 1999 34 ( 1 ): 93-111 ; argues Lapointe guided the more imperialist Mackenzie King through three explosive situations: the Ethiopian crisis of 1935, the Munich crisis of 1938, and the formulation of Ottawa's ' no-neutrality-no-conscription ' pact in 1939.