Events January–June January 31 – Portuguese succession crisis of 1580: The death of Henry, King of Portugal, with no direct heirs, leads to conflict between his potential successors, including King Philip II of Spain and Infanta Catherine, Duchess of Braganza. March 1 – Michel de Montaigne signs the preface to his most significant work, Essays. They are published later this year. March 25 – Iberian Union: King Philip II of Spain becomes King of Portugal under the name Philip I, following the death without heirs of King Henry of Portugal, in a personal union of the crowns, thus maintaining Portuguese independence (in Europe and throughout the Portuguese Empire). The Philippine Dynasty rule lasts until 1640. April 6 – The Dover Straits earthquake occurs. May – The Lipizzan stud is established by Charles II, Archduke of Austria. June – England signs a commercial treaty with the Ottoman Empire. June 11 – Juan de Garay founds Buenos Aires. June 25 – The Book of Concord, a collection of Lutheran confessional documents, is published. July–December July 12 – The Ostrog Bible, the first complete printed Bible translation into a Slavic language (Old Church Slavonic), is first printed at Ostroh in the Polish–Lithuanian Commonwealth (modern-day Ukraine) by Ivan Fyodorov. August 25 – Battle of Alcântara: Spanish armies, led by Fernando Álvarez de Toledo, defending the claim of King Philip II of Spain to the Portuguese throne, defeat the armies of Portuguese claimant António, Prior of Crato. September 26 – Francis Drake returns to Plymouth, England from his voyage of circumnavigation (westbound) on the Golden Hind, the second completed in a continuous voyage, and the first under its original commander. Date unknown The Billy Mitchell volcano, on the island of Bougainville, undergoes a catastrophic eruption (VEI 6). The first session of the Jewish Vaad (Council of Four Lands) is held in Lublin, Poland; 70 delegates of Jewish local qahals meet to discuss taxation, and other issues important to Jewish communities. The Old City of Zamość is established in Poland, by Jan Zamoyski. Jesuit missionaries arrive at the court of Akbar, ruler of the Mughal Empire. A group of English merchants gains the right to trade in Ottoman territory, in return for supplying the sultan with iron, steel, brass and tin for his war with Persia. An influenza pandemic sweeps the world, starting in Asia and moving rapidly through Africa, Europe, and eventually the Americas. More