* 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.

* Festus Mogae ( born 1939 ), former President of Botswana

Festus Gontebanye Mogae ( born 21 August 1939 ) is a Botswana politician who was President of Botswana from 1998 to 2008.

* 1939 – Michael D. Antonovich, American politician

* 1939 – Roy Romanow, Canadian politician

* 1939 – Charlie Rose, American politician ( d. 2012 )

* 1939 – Joseph Lyons, Australian politician, 10th Prime Minister of Australia ( b. 1879 )

* Aleke Banda ( 1939 – 2010 ), Malawian politician

* 1939 – Yael Dayan, Israeli writer and politician

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

* 1939 – Harry Reid, American politician

* 1939 – Tom Hayden, American politician and activist

* 1891 – Vlas Chubar, Soviet politician ( d. 1939 )

* 1939 – Orlando Parga, Puerto Rican politician

* 1939 – Tadahiro Matsushita, Japanese politician ( d. 2012 )

* 2011 – Miltiadis Evert, Greek politician ( b. 1939 )

Gro Harlem Brundtland () ( born Gro Harlem, 20 April 1939 ) is a Norwegian Social democratic politician, diplomat, and physician, and an international leader in sustainable development and public health.

* 1939 – Frank McCloskey, American politician ( d. 2003 )

* 1939 – Ahmet Taner Kışlalı, Turkish politician, journalist, and educator ( d. 1999 )

* 1939 – Brooks Firestone, American businessman and politician

* 1939 – Gabriel Romanus, Swedish politician

* 1939 – László Kovács, Hungarian politician and diplomat

* 1865 – Philipp Scheidemann, German politician, 10th Chancellor of Germany ( d. 1939 )

* 1939 – John Howard, Australian politician, 25th Prime Minister of Australia