* 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 – World War II: Germany and the Soviet Union sign a non-aggression treaty, the Molotov-Ribbentrop Pact.

* 1939 – Nazi Germany mounts a staged attack on the Gleiwitz radio station, creating an excuse to attack Poland the following day thus starting World War II in Europe.

In 1939, coinciding with the start of World War II, Rene Dubos reported the discovery of the first naturally derived antibiotic, gramicidin from B. brevis.

Weil was in Finland when World War II broke out ; he had been traveling in Scandinavia since April 1939.

Armoured trains saw use during the 19th century in the American Civil War ( 1861 – 1865 ), the Franco-Prussian War ( 1870 – 1871 ), the First and Second Boer Wars ( 1880 – 81 and 1899 – 1902 ), the First ( 1914 – 1918 ) and Second World Wars ( 1939 – 1945 ) and the First Indochina War ( 1946 – 1954 ).

* 1939 – World War II: Italy invades Albania.

The Stadium was the scene Lou Gehrig's Farewell Speech in 1939, Don Larsen's perfect game in the 1956 World Series, Roger Maris ' record breaking 61st home run in 1961, and Reggie Jackson's 3 home runs to clinch Game 6 of the 1977 World Series.

During the Sino-Japanese War ( 1937 – 1945 ) and World War II ( 1939 – 1945 ), the Special Research Units of the Imperial Japanese Army, such as Unit 731, conducted human experimentation on thousands of Chinese, among others.

During the First World War the German army used horses for logistics, 1. 4 million of them, in the 1939 – 45 war it used 2. 7 million horses.

* Bloody Sunday ( 1939 ), aka Bromberg Bloody Sunday, a massacre in Bydgoszcz, Poland, at the onset of World War II

The Second World War broke out in 1939 with the German invasion of Poland.

Examples of this style of film include It's a Wonderful World ( 1939 ), The Shop Around the Corner ( 1940 ), Sabrina ( 1954 ), Annie Hall ( 1977 ), When Harry Met Sally ... ( 1989 ), Pretty Woman ( 1990 ), and Four Weddings and a Funeral ( 1994 ).

While most armies still maintained cavalry units at the outbreak of World War II in 1939, significant mounted action was largely restricted to the Polish, Balkan and Soviet campaigns.

There were plans for races at Zandvoort before World War II: the first street race was held on June 3, 1939.

After the outbreak of World War II in 1939, American communists argued that the United States should not get involved in the war on the side of the United Kingdom, since the Molotov-Ribbentrop Pact of nonaggression meant that the Soviet Union was at peace with Germany.

* 1939 – World War II: Pope Pius XII makes a Christmas Eve appeal for peace.

First synthesized in 1874, DDT's insecticidal properties were not discovered until 1939, and it was used with great success in the second half of World War II to control malaria and typhus among civilians and troops.

* 1939 – Indian Muslims observe a " Day of Deliverance " to celebrate the resignations of members of the Indian National Congress over their not having been consulted over the decision to enter World War II with Britain.

Extermination camps ( or death camps ) were camps built by Nazi Germany during the Second World War ( 1939 – 45 ) to systematically kill millions of people by gassing and extreme work under starvation conditions.

* 1939 – 1945: In World War II many countries are occupied by Germany and the Soviet Union, where Esperanto organisations often were prohibited or Esperanto activities were limited in other ways.

Overt alliance with Germany was not possible due to the result of the First World War, but in general the period of 1918 to 1939 was characterised by economic growth and increasing integration to the Western world economy.

* During World War II, the secret protocol in Molotov-Ribbentrop pact enabled Winter War ( 1939 – 40 ), a Soviet attack on Finland.

One result was the creation by the American company MGM of an English studio MGM-British in Hertfordshire, which produced some very successful films, including A Yank at Oxford ( 1938 ) and Goodbye, Mr. Chips ( 1939 ), before World War II intervened.