April 1, 1748: Ruins of Pompeii rediscovered by Spaniard Rocque Joaquin de Alcubierre

April 2, 1453: Mehmed II begins his siege of Constantinople

April 3, 1922: Joseph Stalin appointed General Secretary of the Russian Communist Party by Vladimir Lenin.

April 4, 1968: US civil rights activist Martin Luther King  Jr. assassinated in Memphis, Tennessee

April 5, 1764: British Parliament passes the Sugar Tax on the American colonies, introduced by Prime Minister George Grenville.

April 6, 774: Charles the Great (Charlemagne) confirmed the gift to the Pope of the territories belonging to Ravenna made by his father Pepin the Short at Quiercy-sur-Loire in 753

April 7, 529: First draft of Corpus Juris Civilis (fundamental work in jurisprudence) issued by Eastern Roman Emperor Justinian I.

April 8, 1796: Carl Friedrich Gauss, German mathematician, proves the quadratic reciprocity law (the ability to determine the solvability of any quadratic equation in modular arithmetic)

April 9, 1940: Nazi Germany invades Denmark and Norway, and Denmark surrenders after a six-hour battle

April 10, 1972: US, USSR & 70 other nations agree to ban biological weapons

April 11, 1961: Trial of Adolf Eichmann for war crimes in World War II begins in Jerusalem, Israel

April 12, 1782: Battle at Les Saintes: British fleet under Admiral George Rodney defeats the French fleet under Comte de Grasse off Dominica in the West Indies. Prevents a planned French and Spanish invasion of Jamaica

April 13, 1868: Abyssinian War ends as British and Indian troops capture Magdala and Ethiopian Emperor Tewodros II commits suicide

April 14, 1912: The Titanic hits an iceberg off Newfoundland. 

April 15, 1493: Columbusmeets with King Ferdinand & Isabella in Barcelona.