* 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: Adolf Hitler and Joseph Stalin agree partition of Poland in Molotov-Ribbentrop Pact

That aggressive strategy worked as Germany pulled out of the League of Nations ( 1933 ), rejected the Versailles Treaty and began to re-arm ( 1935 ), won back the Saar ( 1935 ), remilitarized the Rhineland ( 1936 ), formed an alliance (" axis ") with Mussolini's Italy ( 1936 ), sent massive military aid to Franco in the Spanish Civil War ( 1936 – 39 ), seized Austria ( 1938 ), took over Czechoslovakia after the British and French appeasement of the Munich Agreement of 1938, formed a peace pact with Joseph Stalin's Soviet Union in August 1939, and finally invaded Poland in September 1939.

In 1939 Holt's mentor Robert Menzies became Prime Minister after the sudden death of the incumbent Joseph Lyons and the short-term caretaker ministry of Sir Earle Page.

* Hugh Joseph Tallon The concept of self in British and American idealism Catholic University of America Press, 1939

* 1939 – Judge Joseph Force Crater, known as the " Missingest Man in New York ", is declared legally dead.

During all this time, Ribbentrop feuded with various other Nazi leaders ; at one point in August 1939 an armed clash took place between supporters of Ribbentrop and those of Propaganda Minister Joseph Goebbels over the control of a radio station in Berlin that was meant to broadcast German propaganda abroad ( Goebbels claimed exclusive control of all propaganda both at home and abroad whereas Ribbentrop asserted a claim to monopolize all German propaganda abroad ).

During the Molotov – Ribbentrop Pact negotiations, Ribbentrop was overjoyed by a report from his Ambassador in Moscow, Count Friedrich Werner von der Schulenburg, of a speech by the Soviet leader Joseph Stalin before the 18th Party Congress in March 1939 that was strongly anti-Western, which Schulenburg reported meant that the Soviet Union might be seeking an accord with Germany.

On 27 September 1939, Ribbentrop made a second visit to Moscow, where at meetings with the Soviet Foreign Commissar Vyacheslav Molotov and Joseph Stalin, he was forced to agree to revising the Secret Protocols of the Non-Aggression Pact in the Soviet Union's favour, most notably agreeing to Stalin's demand that Lithuania go to the Soviet Union.

Later, in Business Cycles ( 1939 ), Joseph Schumpeter suggested naming the cycles " Kondratieff waves ", in honor of the economist who first noticed them.

* Lash, Joseph P. Roosevelt and Churchill, 1939 – 1941, W. W. Norton and Co, New York, 1976.

Page remained dominant in the party until 1939 and briefly served as an interim Prime Minister between the death of Joseph Lyons and the election of Robert Menzies as his successor, but Page's refusal to serve under Menzies led to his resignation as leader.

* 1939 – Joseph Pitts, American politician

* 1869 – Joseph Duveen, British art dealer ( d. 1939 )

* When Joseph Lyons, prime minister and leader of the United Australia Party ( UAP ), died suddenly in April 1939, the governor-general, Lord Gowrie, called on Sir Earle Page to become caretaker prime minister.

Menzies ' first term as Prime Minister commenced in 1939, after the death in office of the United Australia Party leader Joseph Lyons and a short-term interim premiership by Sir Earle Page.

* 1894 – Joseph Roth, Austrian novelist ( d. 1939 )

However the première of the opera was postponed because Meyerhold was arrested on 20 June 1939 by the NKVD ( Joseph Stalin's Secret Police ), and shot on 2 February 1940.

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

Hitler however cut a deal with Joseph Stalin to divide Eastern Europe ; when Germany did invade Poland in September 1939, Britain and France declared war ; the British Commonwealth followed London's lead.

On 7 April 1939, with the storm clouds of the Second World War gathering in Europe and the Pacific, Joseph Lyons became the first Prime Minister of Australia to die in office.

* September 2 – Joseph Roth, Austrian writer ( d. 1939 )

* September 15 – Joseph Lyons, Premier of Tasmania and Prime Minister of Australia ( d. 1939 )

After the hotel went bankrupt, it was purchased in 1939 by Joseph Gross, Julius Krauss, and David Bard, and these partners managed the hotel together until the early 1970s.