325: The First Council of Nicaea is formally opened, starting the first ecumenical council of the Christian Church.
491: Empress Ariadne marries Anastasius I. The widowed Augusta is able to choose her successor for the Byzantine throne, after Zeno (late emperor) dies of dysentery.
526: An earthquake kills about 250,000 people in what is now Syria and Antiochia.
794: King Æthelberht II of East Anglia visits the royal Mercian court at Sutton Walls, with a view to marrying princess Ælfthryth. He is taken captive and beheaded.
1631: The city of Magdeburg in Germany is seized by forces of the Holy Roman Empire and most of its inhabitants massacred, in one of the bloodiest incidents of the Thirty Years' War.
1813: Napoleon Bonaparte leads his French troops into the Battle of Bautzen in Saxony, Germany, against the combined armies of Russia and Prussia. The battle ends the next day with a French victory.
1861: American Civil War: The state of Kentucky proclaims its neutrality, which will last until September 3 when Confederate forces enter the state. Meanwhile, the State of North Carolina secedes from the Union.
1883: Krakatoa begins to erupt; the volcano explodes three months later, killing more than 36,000 people.
1891: History of cinema: The first public display of Thomas Edison's prototype kinetoscope.
1902: Cuba gains independence from the United States. Tomás Estrada Palma becomes the country's first President.
1927: Treaty of Jeddah: The United Kingdom recognizes the sovereignty of King Ibn Saud in the Kingdoms of Hejaz and Nejd, which later merge to become the Kingdom of Saudi Arabia.
1932: Amelia Earhart takes off from Newfoundland to begin the world's first solo nonstop flight across the Atlantic Ocean by a female pilot, landing in Ireland the next day.
1940: The Holocaust: The first prisoners arrive at a new concentration camp at Auschwitz.
1989: The Chinese authorities declare martial law in the face of pro-democracy demonstrations, setting the scene for the Tiananmen Square massacre.
1990: The first post-Communist presidential and parliamentary elections are held in Romania.
1996: Civil rights: The Supreme Court of the United States rules in Romer v. Evans against a law that would have prevented any city, town or county in the state of Colorado from taking any legislative, executive, or judicial action to protect the rights of gays and lesbians.
2002: The independence of East Timor is recognized by Portugal, formally ending 23 years of Indonesian rule and three years of provisional UN administration (Portugal itself is the former colonizer of East Timor until 1976).
2012: At least 27 people are killed and 50 others injured when a 6.0-magnitude earthquake strikes northern Italy.
2013: An EF5 tornado strikes the Oklahoma City suburb of Moore, killing 24 people and injuring 377 others.