Italian troops cross the Albanian border in the hope of a blitzkrieg against Greece

The castle at Colditz, adapted as a high-security prisoner-of-war camp, receives 140 Polish officers as its first inmates

British aircraft sink three Italian battleships at anchor in Taranto harbour

Coventry suffers a raid of such intensity that the new technique becomes known as carpet bombing

Hungary, Romania and Slovakia sign the Tripartite Pact, joining the war on the German side

The de Havilland Mosquito, a multi-purpose wooden aeroplane widely used by the RAF in World War II, makes its first flight

Adolf Hitler orders preparations to be made for Operation Barbarossa, his planned invasion of the Soviet Union

German armies cross the border to invade Russia on a front from the Baltic to southern Poland

British aviator Amy Johnson is reported missing over the Thames estuary when flying on a mission for the Air Ministry

English composer Michael Tippett completes his oratorio A Child of our Time (not performed until 1944)

Bertolt Brecht's play set in the Thirty Years' War, Mother Courage, has its first performance in Zurich

Henri Matisse, recovering from an operation, develops his technique of gouaches découpées (cut-out patches of painted paper)

Greek soprano Maria Callas sings her first Tosca, in the opera house in Athens

British author Rebecca West publishes an account of Yugoslavia, Black Lamb and Grey Falcon

The Italian navy, defeated off Cape Matapan, ceases to be a significant factor in the Mediterranean

German troops invade and rapidly overrun Yugoslavia

German troops move on from Yugoslavia into Greece, driving a small British force from the mainland across the sea to Crete

In preparation for the invasion of Russia, Adolf Hitler and Heinrich Himmler set up Special Task Commandos (Einsatzkommando) to exterminate Communists and Jews

Rudolf Hess, Hitler's deputy in the Nazi party, flies to Britain on a bizarre secret mission

A Gloster E.28/39 air frame becomes the first craft to fly with a Whittle jet engine

Germany's latest battleship, the Bismarck, is sunk in the Atlantic with the loss of nearly all her 2222 crew

German forces evict the British from the island of Crete after a week-long battle

June 27 - the Communist Party of Yugoslavia appoints Tito to head a guerrilla force to resist the recent German invasion of the country

The systematic shooting of Russian Jews by German Einsatzgruppen is the first step in the development of the Holocaust

Less than four weeks after crossing the Russian border, a German army is within 200 miles of Moscow