March 29 - World War II: British Royal Navy and Royal Australian Navy forces defeat those of the Italian Regia Marina off the Peloponnesus coast of Greece in the Battle of Cape Matapan.
April 1 - The Blockade Runner Badge for German navy is instituted.
April 6 - World War II: Operation Castigo begins. Germany invades the Kingdom of Yugoslavia and Greece.
April 10 - World War II: The Axis Powers in Europe establish the Independent State of Croatia from occupied Yugoslavia with Ante Paveliæ's Ustase fascist insurgents in power.
April 13 - Pact of neutrality between the USSR and Japan is signed.
April 14 - World War II: The Ustashe, a Croatian far-right organization is put in charge of the Independent State of Croatia by the Axis Powers after the Axis Operation 25 invasion. In addition, Rommel attacks Tobruk.
April 15 - In the Belfast Blitz, two-hundred bombers of the German Air Force (Luftwaffe) attack Belfast, Northern Ireland killing one thousand people.
April 16 - World War II: The Italian convoy Duisburg, directed to Tunisia, is attacked and destroyed by British ships.
April 16 - Bob Feller of the Cleveland Indians throws the only Opening Day no-hitter in the history of Major League Baseball, beating the Chicago White Sox 1-0.
April 17 - World War II: The Kingdom of Yugoslavia surrenders to Germany.
April 23 - World War II: Greek government and King George II evacuate Athens before the attacking Wehrmacht.
April 27 - World War II: German troops enter Athens.
May 1 - World War II: German forces launch Operation Mercury the largest airborne invasion to date in their bid to capture Crete.
May 1 - World War II: German forces launch a major attack on Tobruk.
May 6 - At California's March Field, Bob Hope performs his first USO show.
May 9 - World War II: The German submarine U-110 is captured by the Royal Navy. On board is the latest Enigma cryptography machine which Allied cryptographers later use to break coded German messages.
May 10 - World War II: The House of Commons in London is damaged by the Luftwaffe in an air raid.
May 10 - World War II: Rudolf Hess parachutes into Scotland in order to try and negotiate a peace deal between the United Kingdom and Germany.
May 12 - Konrad Zuse presents the Z3, the world's first working programmable, fully automatic computer, in Berlin.
May 13 - World War II: Yugoslav royal colonel Dragoljub Mihailović starts fighting with German occupation troops, beginning the Serbian resistance.
May 15 - Baseball player Joe DiMaggio of the New York Yankees starts his record-breaking 56-game hitting streak.
May 20 - World War II: Battle of Crete – German paratroops invade Crete.
May 21 - World War II: 950 miles off the coast of Brazil, the freighter SS Robin Moor becomes the first American ship sunk by a German U-boat.
May 24 - World War II: In the North Atlantic, the German Battleship Bismarck sinks the HMS Hood killing all but three crewmen on what was the pride of the Royal Navy.
May 27 - World War II: U.S. President Franklin D. Roosevelt proclaims an "unlimited national emergency".
May 27 - World War II: The German battleship Bismarck is sunk in the North Atlantic killing almost 2,100 men.
July 4 - Nazi Germans massacre Polish scientists and writers in the captured Polish city of Lwów.
July 5 - World War II: German troops reach the Dniepr River.
July 7 - World War II: U.S. forces land in Iceland to forestall an invasion by Germany.
July 7 - World War II: Beirut is occupied by Free France and British troops.
July 10 - Jedwabne Pogrom is a massacre of Jewish people living in and near the village of Jedwabne in Poland.
July 13 - World War II: Montenegrins start popular uprising against the Axis Powers (Trinaestojulski ustanak).
July 20 - Soviet leader Joseph Stalin consolidates the Commissariats of Home Affairs and National Security to form the NKVD and names Lavrenti Beria its chief.
July 26 - World War II: In response to the Japanese occupation of French Indo-China, US President Franklin D. Roosevelt orders the seizure of all Japanese assets in the United States.
July 27 - Japanese troops occupy French Indo-China.
July 31 - Holocaust: under instructions from Adolf Hitler, Nazi official Hermann Göring, orders SS General Reinhard Heydrich to "submit to me as soon as possible a general plan of the administrative material and financial measures necessary for carrying out the desired final solution of the Jewish question."
August 16 - HMS Mercury, Royal Navy Signals School and Combined Signals School opens at Leydene, near Petersfield, Hampshire, England.
August 18 - Adolf Hitler orders a temporary halt to Nazi Germany's systematic euthanasia of the mentally ill and the handicapped due to protests.
August 22 - World War II: German troops reach Leningrad, leading to the siege of Leningrad.
August 30 - World War II: Siege of Leningrad begins.
September 8 - World War II: Siege of Leningrad begins. German forces begin a siege against the Soviet Union's second-largest city, Leningrad.
September 11 - Ground is broken for the construction of The Pentagon.
September 11 - World War II: The U.S. Navy is ordered to attack German U-boats.
September 11 - Charles Lindberg's Des Moines Speech accusing the British, Jews and the Roosevelt administration of pressing for war with Germany.
September 16 - World War II: concerned that Reza Pahlavi the Shah of Persia was to align his petroleum-rich country with Germany during World War II, the United Kingdom and the USSR invade Iran in late August and force him to resign in favor of his son, Mohammad Reza Pahlavi.
September 17 - World War II: A decree of the Soviet State Committee of Defense, restoring Vsevobuch in the face of the Great Patriotic War, is issued
September 22 - World War II: On Jewish New Year Day, the German SS murder 6,000 Jews in Vinnytsya, Ukraine. Those were the survivors of the previous killings that took place a few days earlier in which about 24,000 Jews were executed.
September 23 - World War II: The first gas murder experiments are conducted at Auschwitz.
September 27 - The SS Patrick Henry is launched becoming the first of more than 2,700 Liberty ships.
September 27 - Foundation of EAM (National Liberation Front) in Greece.
September 28 - Major League Baseball: Ted Williams of the Boston Red Sox finishes the season with a batting average of .406. He is the latest major league player to have a batting average of .400 or better.
September 29 - World War II: Holocaust in Kiev, Ukraine: German Einsatzgruppe C starts Babi Yar massacre. According to the Einsatzgruppen Operational Situation Report No. 101, at least 33,771 Jews from Kiev and its suburbs were killed at Babi Yar on September 29
October 2 - World War II: In Operation Typhoon, Germany begins an all-out offensive against Moscow.
October 8 - World War II: In their invasion of the Soviet Union, Germany reaches the Sea of Azov with the capture of Mariupol.
October 9 - A coup in Panama declares Ricardo Adolfo de la Guardia Arango the new president.
October 11 - Beginning of the National Liberation War of Macedonia.
October 17 - For the first time in World War II, a German submarine attacks an American ship.
October 20 - World War II: Thousands of civilians in Kragujevac in German-occupied Serbia are killed in the Kragujevac massacre.
October 22 - French hero of the resistance Guy Môquet is executed by the Germans, along with 29 other hostages as a retaliation for a killed German officer.
October 23 - World War II: Field Marshal Georgy Zhukov takes command of Red Army operations to prevent the further advance into Russia of German forces and to prevent the Wehrmacht from capturing Moscow.
October 23 - Odessa Massacre: 19,000 Jews are shot or burned alive at Dalnik in Odessa, by Romanian and German troops. The next day, another 10,000 Jews are killed. Romanian Lieutenant-Colonel Nicolae Deleanu administered the executions.
October 29 - Holocaust: In the Kaunas Ghetto over 10,000 Jews are shot by German occupiers at the Ninth Fort, a massacre known as the "Great Action".
October 30 - World War II: Franklin Delano Roosevelt approves U.S. $1 billion in Lend-Lease aid to the Allied nations.
October 30 - 1,500 Jews from Pidhaytsi (in western Ukraine) are sent by Nazis to Belzec extermination camp.
October 31 - After 14 years of work, drilling is completed on Mount Rushmore.
October 31 - World War II: The destroyer USS Reuben James is torpedoed by a German U-boat near Iceland, killing more than 100 United States Navy sailors. It is the first U.S. Navy vessel sunk by enemy action in WWII.
October 31 - A fire in a clothing factory in Huddersfield, England kills 49
November 1 - American photographer Ansel Adams takes a picture of a moonrise over the town of Hernandez, New Mexico that would become one of the most famous images in the history of photography.
November 6 - World War II: Soviet leader Joseph Stalin addresses the Soviet Union for only the second time during his three-decade rule. He states that even though 350,000 troops were killed in German attacks so far, the Germans had lost 4.5 million soldiers and that Soviet victory was near.
November 7 - World War II: Soviet hospital ship Armenia was sunk by German planes while evacuating refugees and wounded military and staff of several Crimea’s hospitals. It is estimated that over 5,000 people died in the sinking.
November 8 - The Albanian Communist Party is founded.
November 12 - World War II: Temperatures around Moscow drop to -12 ° C and the Soviet Union launches ski troops for the first time against the freezing German forces near the city.
November 12 - The Soviet cruiser "Chervona Ukraina" is destroyed during the Battle of Sevastopol.
November 13 - World War II: The aircraft carrier HMS Ark Royal is torpedoed by U 81, sinking the next day.
November 14 - World War II: The aircraft carrier HMS Ark Royal sinks due to torpedo damage from U-81 sustained on November 13.
November 15 - Holocaust: SS chief Heinrich Himmler orders the arrest and deportation to concentration camps of all homosexuals in Germany, with the exception of certain top Nazi officials.
November 19 - World War II: Battle between HMAS Sydney and HSK Kormoran. The two ships sink each other off the coast of Western Australia, with the loss of 645 Australians and about 77 German seamen.
November 24 - World War II: The United States grants Lend-Lease to the Free French.
December 7 - Holocaust (Shoah): Extermination of Jewish people at the death camp of Chelmno begins.
December 8 - World War II: The Japanese invade the British Crown Colony of Hong Kong, Malaya and the Dutch East Indies. They also invade the portions of Shanghai administered by European powers and bomb American bases in the Philippines. Because of the time difference, these events