The German occupation of Luxembourg during World War I begins. 1916 – World War I: Austrian sabotage causes the sinking of the Italian battleship Leonardo da Vinci in Taranto. 1918 – The first general strike in Canadian history takes place in Vancouver. 1922 – A typhoon hits Shantou, Republic of China, killing more than 50,000 people. 1923 – Vice President Calvin Coolidge becomes U.S. President upon the death of President Warren G. Harding. 1932 – The positron (antiparticle of the electron) is discovered by Carl D. Anderson. 1934 – Reichskanzler Adolf Hitler becomes Führer of Germany following the death of President Paul von Hindenburg. 1937 – The Marihuana Tax Act of 1937 is passed in America, the effect of which is to render marijuana and all its by-products illegal. 1939 – Albert Einstein and Leo Szilard write a letter to Franklin D. Roosevelt, urging him to begin the Manhattan Project to develop a nuclear weapon. 1943 – The Holocaust: Jewish prisoners stage a revolt at Treblinka, one of the deadliest of Nazi death camps where approximately 900,000 persons were murdered in less than 18 months. 1943 – World War II: The Motor Torpedo Boat PT-109 is rammed by the Japanese destroyer Amagiri and sinks. Lt. John F. Kennedy, future U.S. president, saves all but two of his crew. 1944 – ASNOM: Birth of the Socialist Republic of Macedonia, celebrated as Day of the Republic in North Macedonia. 1944 – World War II: The largest trade convoy of the world wars arrives safely in the Western Approaches. 1945 – World War II: End of the Potsdam Conference. 1947 – A British South American Airways Avro Lancastrian airliner crashes into a mountain during a flight from Buenos Aires, Argentina to Santiago, Chile. The wreckage would not be found until 1998. 1968 – An earthquake hits Casiguran, Aurora, Philippines killing more than 270 people and wounding 261. 1973 – A flash fire kills 51 people at the Summerland amusement centre at Douglas, Isle of Man. 1980 – A bomb explodes at the railway station in Bologna, Italy, killing 85 people and wounding more than 200. 1982 – The Helsinki Metro, the first rapid transit system of Finland, is opened to the general public. 1985 – Delta Air Lines Flight 191, a Lockheed L-1011 TriStar, crashes at Dallas/Fort Worth International Airport killing 137. 1989 – Pakistan is re-admitted to the Commonwealth of Nations after