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Magdeburg is sacked by an Imperial army.

Gustav II Adolf of Sweden, victorious in the Battle of Breitenfeld.

Dutch and Spanish ships in the Battle of the Slaak.

Year 1631 (MDCXXXI) was a common year starting on Wednesday (link will display the full calendar) of the Gregorian calendar and a common year starting on Saturday of the 10-day slower Julian calendar.

Events[link]

January–June[link]

• January 23 – Thirty Years' War: Sweden and France sign the Treaty of Bärwalde, a military alliance in which France provides funds for the Swedish army invading northern Germany.
• February 5 – Roger Williams emigrates to Boston.
• February 16 – Gustav Adolf Secondary School is founded in Tallinn, Estonia by Swedish king Gustav II Adolf.
• April 13 – Thirty Years' War: Gustav Adolf of Sweden defeats an imperial garrison at the city of Frankfurt an der Oder.
• May 10 – Thirty Years' War: After a two month siege, an Imperial army under the command of Tilly storms the German city of Magdeburg and brutally sacks it, massacring over 20,000 inhabitants. Shocked by the massacre, many protestant states in the Holy Roman Empire decide to ally with Gustav Adolf of Sweden and support his ongoing invasion.
• May 18 – In Dorchester, Massachusetts, John Winthrop takes the oath of office and becomes the first Governor of Massachusetts.
• May 30
  • La Gazette, the first French newspaper, was founded.
  • Thirty Years' War: Bavaria and France sign the Treaty of Fontainebleau, forming a secret alliance. The secret alliance does not last long, however.
• June 19 – War of Mantuan Succession: The Treaty of Cherasco is signed, ending the War of Mantuan Succession.
• June 20 – Algerian pirates sack Baltimore, County Cork in Ireland.

July–December[link]

• July 16 – The city of Würzburg is taken by Gustav Adolf of Sweden, putting an end to the Würzburg witch trials, but not before an estimated 900 people from the city and its environs had been burned at the stake for witchcraft.
• July 22 – Thirty Years' War: Tilly defeats Gustav Adolf of Sweden at the Battle of Werben, but not decisively.
• End of August – Thirty Years' War: Running out of supply, Tilly is forced to send his army into Electoral Saxony in order to secure supplies, as well as to force a reaction from John George, Elector of Saxony and Gustav Adolf of Sweden.
• September 11 – Thirty Years' War: As a result of Tilly's invasion, John George, Elector of Saxony, who had until now stayed neutral, allies with Gustav Adolf of Sweden in order to drive the Imperial army out of Saxony.
• September 12 – Eighty Years' War: A Spanish fleet under the command of admiral Antonio de Oquendo defeats a Dutch fleet off the coast of Brazil in the Battle of Albrolhos.
• September 12 and 13 – Eighty Years' War: A Spanish fleet carrying an invasion force is intercepted and almost completely destroyed by a Dutch fleet in the Battle of the Slaak.
• September 17 – Thirty Years' War: In the Battle of Breitenfeld, Tilly's imperial army is decisively defeated by Gustav II Adolf of Sweden, shattering the imperial army of the Holy Roman Empire and marking the first significant victory for the Protestants in the war.
• October 10 – Thirty Years' War: A Saxon army takes over Prague.
• December 23 – Thirty Years' War: Gustav Adolph of Sweden takes the city of Mainz without any resistance.

Date unknown[link]

• Moses Amyraut's Traite des Religions is published.
• The bell "Emmanuel" in Notre Dame de Paris is recast.
• The Taj Mahal's construction is started (it is finished in 1653).
• Mount Vesuvius erupts in Pompeii.
• First English settlement by William Claiborne within the State of Maryland, U.S.A.

Births[link]

• January 1 – Katherine Philips, Anglo-Welsh poet (d. 1664)
• February 20 – Thomas Osborne, 1st Duke of Leeds, English statesman (d. 1712)
• March 16 – René Le Bossu, French critic (d. 1680)
• May 2 – Sir John Murray, 1st Marquess of Atholl (d. 1703)
• July 15 – Jens Juel, Danish diplomat (d. 1700)
• August 19 – John Dryden, English writer (d. 1700)
• September 3 – William Stoughton, American judge at the Salem witch trials (d. 1701)
• November 4 – Mary, Princess Royal and Princess of Orange (d. 1660)
• December 14 – Lady Anne Finch Conway, English philosopher (d. 1679)

Deaths[link]

• January 1 – Thomas Hobson, English carrier and origin of the phrase "Hobson's choice" (b. 1544)
• January 3 – Michelagnolo Galilei, Italian composer and lutenist younger brother of Galileo Galilei (b. 1575)
• March 31 – John Donne, English writer and prelate (b. 1572)
• May 6 – Robert Bruce Cotton, English politician (b. 1570)
• June 17 – Mumtaz Mahal, favorite wife of Shah Jahan (b. 1593)
• June 21 – John Smith of Jamestown, English soldier and colonist (b. 1580)
• July 19 – Cesare Cremonini, Italian philosopher (b. 1550)
• July 28 – Guillén de Castro y Bellvis, Spanish dramatist (b. 1569)
• October 14 – Sophie of Mecklenburg-Güstrow, Queen and regent of Denmark (b. 1557)
• December 23 – Michael Drayton, English poet (b. 1563)

References[link]