thumb|Soldiers of the Lithuanian People's Army carrying the Soviet propaganda posters, August 1940 August 1 – WWII: British submarine is sunk in the English Channel, by what is much later discovered to be a mine. August 3 – The Lithuanian SSR is annexed into the Soviet Union, followed by the Latvian SSR on August 5 and the Estonian SSR August 6, just seven weeks after their occupation. Ethnic Germans will be deported to Germany. August 3–19 – WWII: The Italian conquest of British Somaliland is completed. August 4 – U.S. Gen. John J. Pershing, in a nationwide radio broadcast, urges all-out aid to Britain in order to defend the Americas, while Charles Lindbergh speaks to an isolationist rally at Soldier Field in Chicago. August 8 – WWII: German general Wilhelm Keitel signs the Aufbau Ost directive, which eventually leads to the invasion of the Soviet Union. August 10 – WWII: British armed merchant cruiser is torpedoed off Malin Head, Ireland, by German submarine U-56. August 13 – WWII: Luftwaffe Adlertag ("Eagle Day") strike on southern England occurs, starting the rapid escalation of the Battle of Britain. August 15 – Italy, without having declared war on Greece, sinks the Greek boat Elli (Έλλη). August 18 WWII: "The Hardest Day" in the Battle of Britain: Both sides lose more aircraft combined on this day than at any other point during the campaign, without the Luftwaffe achieving dominance over RAF Fighter Command. The Prince Edward, Duke of Windsor, is installed as Governor of the Bahamas. August 20 WWII: Winston Churchill pays tribute in the House of Commons of the United Kingdom to the Royal Air Force fighter pilots: "Never in the field of human conflict was so much owed by so many to so few." Leon Trotsky is attacked with an ice axe in his Mexico home by NKVD agent Ramón Mercader. August 24 – Howard Florey and a team including Ernst Chain and Norman Heatley at the Sir William Dunn School of Pathology, University of Oxford, publish their laboratory results showing the in vivo bactericidal action of penicillin. They have also purified the drug. August 25 – WWII: The first Bombing of Berlin is carried out, by the British Royal Air Force. August 26 – WWII: Chad is the first French colony to proclaim its support for the Allies. August 30 – Second Vienna Award: Germany and Italy compel Romania to cede half of Transylvania to Hungary. August 31 WWII: Texel Disaster: Two British Royal Navy destroyers are sunk by running into a minefield off the coast of the occupied Netherlands with the loss of around 400 men, 300 of them dead. British film stars Laurence Olivier and Vivien Leigh are married at the San Ysidro Ranch in California.
thumb|Soldiers of the Lithuanian People's Army carrying the Soviet propaganda posters, August 1940 August 1 – WWII: British submarine is sunk in the English Channel, by what is much later discovered to be a mine. August 3 – The Lithuanian SSR is annexed into the Soviet Union, followed by the Latvian SSR on August 5 and the Estonian SSR August 6, just seven weeks after their occupation. Ethnic Germans will be deported to Germany. August 3–19 – WWII: The Italian conquest of British Somaliland is completed. August 4 – U.S. Gen. John J. Pershing, in a nationwide radio broadcast, urges all-out aid to Britain in order to defend the Americas, while Charles Lindbergh speaks to an isolationist rally at Soldier Field in Chicago. August 8 – WWII: German general Wilhelm Keitel signs the Aufbau Ost directive which eventually leads to the invasion of the Soviet Union. August 10 – WWII: British armed merchant cruiser is torpedoed off Malin Head, Ireland, by German submarine U-56. August 13 – WWII: L,uftwaffe Adlertag ("Eagle Day") strike on southern England occurs, starting the rapid escalation of the Battle of Britain. August 15 – Italy, without having declared war on Greece, sinks the Greek boat Elli (Έλλη). August 18 WWII: "The Hardest Day" in the Battle of Britain: Both sides lose more aircraft combined on this day than at any other point during the campaign, without the Luftwaffe achieving dominance over RAF Fighter Command. The Prince Edward, Duke of Windsor, is installed as Governor of the Bahamas. August 20 WWII: Winston Churchill pays tribute in the House of Commons of the United Kingdom to the Royal Air Force fighter pilots: "Never in the field of human conflict was so much owed by so many to so few." Leon Trotsky is attacked with an ice axe in his Mexico home by NKVD agent Ramón Mercader. August 24 – Howard Florey and a team including Ernst Chain and Norman Heatley at the Sir William Dunn School of Pathology, University of Oxford, publish their laboratory results showing the in vivo bactericidal action of penicillin. They have also purified the drug. August 25 – WWII: The first Bombing of Berlin is carried out, by the British Royal Air Force. August 26 – WWII: Chad is the first French colony to proclaim its support for the Allies. August 30 – Second Vienna Award: Germany and Italy compel Romania to cede half of Transylvania to Hungary. August 31 WWII: Texel Disaster: Two British Royal Navy destroyers are sunk by running into a minefield off the coast of the occupied Netherlands with the loss of around 400 men, 300 of them dead. British film stars Laurence Olivier and Vivien Leigh are married at the San Ysidro Ranch in California.