April 1527 – Byzantine Emperor Justin I names his nephew Justinian I as co-ruler and successor to the throne. 1081 – Alexios I Komnenos overthrows the Byzantine emperor Nikephoros III Botaneiates, and, after his troops spend three days extensively looting Constantinople, is formally crowned on April 4. 1572 – In the Eighty Years' War, the Watergeuzen capture Brielle from the Seventeen Provinces, gaining the first foothold on land for what would become the Dutch Republic.
June 281098 – Fighters of the First Crusade defeat Kerbogha of Mosul at the battle of Antioch. 1360 – Muhammed VI becomes the tenth Nasrid king of Granada after killing his brother-in-law Ismail II. 1461 – Edward, Earl of March, is crowned King Edward IV of England. 1495 – A French force heavily defeats a much larger Neapolitan and Spanish army at the battle of Seminara, leading to the creation of the Tercios by Gonzalo de Córdoba. 1519 – Charles V is elected Emperor of the Holy Roman Empire.
July 16622 – The Hijrah of Muhammad begins, marking the beginning of the Islamic calendar. 997 – Battle of Spercheios: Bulgarian forces of Tsar Samuel are defeated by a Byzantine army under general Nikephoros Ouranos at the Spercheios River in Greece. 1054 – Three Roman legates break relations between Western and Eastern Christian Churches through the act of placing a Papal bull (of doubtful validity) of Excommunication on the altar of Hagia Sophia during Saturday afternoon divine liturgy.
January 23393 – Roman emperor Theodosius I proclaims his eight-year-old son Honorius co-emperor. 971 – Using crossbows, Song dynasty troops soundly defeat a war elephant corps of the Southern Han at Shao. 1264 – In the conflict between King Henry III of England and his rebellious barons led by Simon de Montfort, King Louis IX of France issues the Mise of Amiens, a one-sided decision in favour of Henry that later leads to the Second Barons' War.
August 24367 – Gratian, son of Roman Emperor Valentinian I, is named co-Augustus at the age of eight by his father. 394 – The Graffito of Esmet-Akhom, the latest known inscription in Egyptian hieroglyphs, is written. 410 – The Visigoths under king Alaric I begin to pillage Rome. 1185 – Sack of Thessalonica by the Normans. 1200 – King John of England, signer of the first Magna Carta, marries Isabella of Angoulême in Angoulême Cathedral. 1215 – Pope Innocent III issues a bull declaring Magna Carta invalid.
April 9193 – The distinguished soldier Septimius Severus is proclaimed emperor by the army in Illyricum. 475 – Byzantine Emperor Basiliscus issues a circular letter (Enkyklikon) to the bishops of his empire, supporting the Monophysite christological position. 537 – Siege of Rome: The Byzantine general Belisarius receives his promised reinforcements, 1,600 cavalry, mostly of Hunnic or Slavic origin and expert bowmen. He starts, despite shortages, raids against the Gothic camps and Vitiges is forced into a stalemate.
May 1028 BC – A sunspot is observed by Han dynasty astronomers during the reign of Emperor Cheng of Han, one of the earliest dated sunspot observations in China. 1291 – Scottish nobles recognize the authority of Edward I of England pending the selection of a king. 1294 – Temür, Khagan of the Mongols, is enthroned as Emperor of the Yuan dynasty. 1497 – Amerigo Vespucci allegedly leaves Cádiz for his first voyage to the New World. 1503 – Christopher Columbus visits the Cayman Islands and names them Las Tortugas after the numerous turtles there.
May 171395 – Battle of Rovine: The Wallachians defeat an invading Ottoman army. 1521 – Edward Stafford, 3rd Duke of Buckingham, is executed for treason. 1527 – Pánfilo de Narváez departs Spain to explore Florida with 600 men – by 1536 only four survive. 1536 – George Boleyn, 2nd Viscount Rochford and four other men are executed for treason. 1536 – Henry VIII and Anne Boleyn's marriage is annulled. 1590 – Anne of Denmark is crowned Queen of Scotland. 1642 – Paul de Chomedey, Sieur de Maisonneuve founds the Ville Marie de Montréal.
May 21293 – Roman Emperors Diocletian and Maximian appoint Galerius as Caesar to Diocletian, beginning the period of four rulers known as the Tetrarchy. 878 – Syracuse, Sicily, is captured by the Muslim Aghlabids after a nine-month siege. 879 – Pope John VIII gives blessings to Branimir of Croatia and to the Croatian people, considered to be international recognition of the Croatian state. 996 – Sixteen-year-old Otto III is crowned Holy Roman Emperor. 1349 – Dušan's Code, the constitution of the Serbian Empire, is enacted by Dušan the Mighty.
March 10241 BC – First Punic War: Battle of the Aegates: The Romans sink the Carthaginian fleet bringing the First Punic War to an end. 298 – Roman Emperor Maximian concludes his campaign in North Africa and makes a triumphal entry into Carthage. 947 – The Later Han is founded by Liu Zhiyuan. He declares himself emperor. 1496 – After establishing the city of Santo Domingo, Christopher Columbus departs for Spain, leaving his brother in command. 1535 – Spaniard Fray Tomás de Berlanga, the fourth Bishop of Panama, discovers the Galápagos Islands by chance on his way to Peru.
