April 12

• April 12, 1204
  Combined forces of Franks and Venetians led by Boniface of Montferrat occupy and plunder Christian city of Constantinople during the Fourth Crusade instead of planned conquest of Muslim-controlled Jerusalem
• April 12, 1606
  England's King James I decreed the design of the original Union Flag, also referred to as the Union Jack, which combined the flags of England and Scotland
• April 12, 1770
  British Parliament repeal the Townsend Acts that put duties on certain products imported to the US
• April 12, 1782
  The British navy win its only naval engagement against the colonists in the American Revolution at the Battle of the Saintes in the West Indies off Dominica
• April 12, 1787
  Philadelphia's Free Africa Society, the first black mutual aid society in the city, is organized by free blacks Richard Allen and Absalom Jones
• April 12, 1798
  French government proclaims Helvetic Republic in occupied Old Swiss Confederacy
• April 12, 1861
  Shore batteries of Confederacy formed by seven Southern slave states, under General P. G. T. Beauregard open fire on US-held Fort Sumter in South Carolina's Charleston Bay, triggering American Civil War
• April 12, 1877
  British annex Transvaal, in South Africa, to resolving the border dispute between the Boers and the Zulus
• April 12, 1927
  Chiang Kai-shek, an influential member of the Kuomintang, the Chinese Nationalist Party, begins counter revolution against Communist Party in Shanghai, starting a full-scale purge of Communists in all areas
• April 12, 1927
  The United Kingdom of Great Britain and Ireland officially becomes the United Kingdom of Great Britain and Northern Ireland with commencement of Royal and Parliamentary Titles Act
• April 12, 1940
  Italy annexes Albania
• April 12, 1945
  Vice President Harry S. Truman becomes President of the United States after the death of Franklin D. Roosevelt
• April 12, 1955
  Researchers announce results of year-long Jonas Salk's polio vaccine trials, that the vaccine is safe and effective
• April 12, 1961
  Yuri Gagarin, a Soviet cosmonaut, becomes the first person in space after his Vostok spacecraft completes an orbit of the Earth
• April 12, 1967
  Astronauts Gus Grissom, Ed White and Roger Chaffee die in the NASA Apollo 1 fire during rehearsal test
• April 12, 1980
  Samuel Doe takes over Liberia and President William R. Tolbert among 27 others are killed in a coup d'etat, ending over 130 years of democratic presidential succession in that country
• April 12, 1981
  First orbital flight of the Space Shuttle, a reusable Earth orbital spacecraft system, is completed by Space Shuttle Columbia
• April 12, 1982
  A 200-mile 'total exclusion zone' around the Falklands proclaimed by the United Kingdom comes into effect
• April 12, 1992
  The Euro Disney Resort, featuring the Euro Disneyland park with six hotels with 5200 rooms and five themed lands, opens in Marne-la-Vallee, France, east of Paris
• April 12, 2011
  Japan raises the nuclear damage level of the Fukushima reactor to INES Level 7, same category as Chernobyl in the Ukraine
• April 12, 2012
  Mutinous soldiers in Guinea-Bissau stage a coup d'etat and take control of the capital city, Bissau, and arrest interim President Raimundo Pereira and leading presidential candidate Carlos Gomes Junior in the midst of a presidential election campaign