* 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 – Cesare Maniago, Canadian ice hockey player

So also Katowice's Bishop Adamski was deposed as apostolic administrator for the Catholic parishes in Zaolzie and on 23 December 1939 Cesare Orsenigo, nuncio to Germany, returned them to their original archdioceses of Breslau or Olomouc, respectively, with effect of 1 January 1940.

The city of Asmara had a population of 98, 000, of which 53, 000 were Italians according to the Italian census of 1939.

Hoxha was dismissed from his teaching post following the 1939 Italian invasion for refusing to join the Albanian Fascist Party.

In October 1939 Mussolini had considered making a public statement to the Italian people that would announce Fascist Italy's abandonment of hostility to the ideology of Stalin's Soviet Union by claiming that Stalin's regime had effectively dissolved Bolshevism and that it had been replaced by a Slavic fascism.

Prior to rising to power, from 1939 to 1941, Peron had developed a deep admiration of Italian Fascism and modelled his economic policies on Italian Fascist economic policies.

He promoted a huge colonization of Italians in Libya: total native Italian population for Libya was 110, 575 out of a total population of 915, 440 in 1939

Indeed in 1939, laws were passed that allowed Muslims to be permitted to join the National Fascist Party and in particular the Muslim Association of the Lictor ( Associazione Musulmana del Littorio ), and the 1939 reforms allowed the creation of Libyan military units within the Italian army.

Total native Italian population for Libya was 110, 575 out of a total population of 915, 440 in 1940 ( General Staff War Office 1939, 165 / b ).

In April 1939, the Italian threat suddenly loomed closer, as Italy annexed Albania, whereupon Britain publicly guaranteed Greece's borders.

Despite some insignificant resistance, especially at Durrës, Italy invaded Albania on 7 April 1939 and took control of the country, with the Italian Fascist dictator Benito Mussolini proclaiming Italy's figurehead King Victor Emmanuel III of Italy as King of Albania.

After Hitler invaded Czechoslovakia ( 15 March 1939 ) without notifying Mussolini in advance, the Italian dictator decided to proceed with his own annexation of Albania.

The National Liberation War of the Albanian people started with the Italian invasion in Albanian on 7 April 1939 and ended on 28 November 1944.

* 1939 – Mariele Ventre, Italian singer and conductor ( d. 1995 )

On 23 April 1939 the Turkish Foreign Minister Şükrü Saracoğlu told the British Ambassador of his nation's fears of Italian claims of the Mediterranean as Mare Nostrum and German control of the Balkans, and suggested an Anglo-Soviet-Turkish alliance as the best way of countering the Axis.

Along the same lines, Ribbentrop told the Italian Foreign Minister Count Galeazzo Ciano on 5 May 1939 " It is certain that within a few months not one Frenchman nor a single Englishman will go to war for Poland ".

On 11 August 1939, Ribbentrop met the Italian Foreign Minister, Count Galeazzo Ciano, and the Italian Ambassador to Germany, Count Bernardo Attolico, in Salzburg.

As soon as the news broke in the morning of 1 September 1939 that Germany had invaded Poland, the Italian dictator Benito Mussolini launched another desperate peace mediation plan intended to stop the German-Polish war from becoming a world war.

In the Second World War ( 1939 – 45 ) Kenya became an important British military base for successful campaigns against Italy in the Italian Somaliland and Ethiopia.

Moreover, the pact erased the legal distinction between war and peace since the signatories, having renounced the use of war began to wage wars without declaring them as evidenced by the U. S. intervention in Central America, the Japanese invasion of Manchuria in 1931, the Italian invasion of Abyssinia in 1935, the Soviet invasion of Finland in 1939, and the German and Soviet Union invasions of Poland.

* 1939 – Albanian fascist leader Tefik Mborja is appointed as member of the Italian Chamber of Fasces and Corporations.

* 1939 – Giovanni Falcone, Italian magistrate and Mafia victim ( d. 1992 )