On This Day: June 12th

First Anglo-Dutch War: The Battle of the Gabbard begins, lasting until the following day.

The Westminster Assembly is convened by the Parliament of England, without the assent of Charles I, in order to restructure the Church of England.

The city of Helsinki, Finland (belonging to Sweden at the time) is founded by King Gustav I of Sweden.

Hundred Years' War: On the second day of the Battle of Jargeau, Joan of Arc leads the French army in their capture of the city and the English commander, William de la Pole, 1st Duke of Suffolk.

Armagnac-Burgundian Civil War: Parisians slaughter sympathizers of Bernard VII, Count of Armagnac, along with all prisoners, foreign bankers, and students and faculty of the College of Navarre.

Peasants' Revolt: In England, rebels assemble at Blackheath, just outside London.

At the instigation of Louis IX of France, an inter-faith debate, known as the Disputation of Paris, starts between a Christian monk and four rabbis.

The Ghurid general Qutb ud-Din Aibak founds the Delhi Sultanate.

Constantine IX Monomachos is crowned as Byzantine Emperor, one day after is marriage to Empress Zoe Porphyrogenita.

Battle of Augsburg: The Hungarians defeat the East Frankish army under King Louis the Child, using the famous feigned retreat tactic of the nomadic warriors.