- August 9, 0048 BC – Caesar’s civil war: Battle of Pharsalus – Julius Caesar decisively defeats Pompey at Pharsalus and Pompey flees to Egypt.
- August 9, 0378 Gothic War: Battle of Adrianople – A large Roman army led by Emperor Valens is defeated by the Visigoths in present-day Turkey. Valens is killed along with over half of his army.
- August 9, 0681 “Bulgaria is founded as a Khanate on the south bank of the Danube, after defeating the Byzantine armies of Emperor Constantine IV south of the Danube delta.”
- August 9, 1048 “Pope Damasus II dies in Rome, after reigning for only 23 days.”
- August 9, 1173 “Construction of the Tower of Pisa begins, and it takes two centuries to complete.”
- August 9, 1483 Opening of the Sistine Chapel
- August 9, 1638 Jonas Bronck of Holland becomes first European settler in the Bronx
- August 9, 1666 “Rear Admiral Robert Holmes leads a raid on the Dutch island of Terschelling, destroying 150 merchant ships in the Vlie estuary, and pillaging the town of West-Terschelling, an act later knkown as “”Holmes’s Bonfire””.”
- August 9, 1673 Dutch recapture NY from English; regained by English in 1674
- August 9, 1778 Capt Cook passes through Bering Strait
- August 9, 1786 First ascent of Mt Blanc
- August 9, 1790 Columbia becomes first US flagged ship to voyage around the world
- August 9, 1803 First horses arrive in Hawaii
- August 9, 1810 Napoleon annexes Westphalia as part of the First French Empire.
- August 9, 1831 First US steam engine train run
- August 9, 1842 US-Canada border defined
- August 9, 1842 “Webster-Ashburton Treaty is signed, establishing the United States-Canada border east of the Rocky Mountains.”
- August 9, 1848 Barnburners (anti-slavery) party merges with the Free Soil Party
- August 9, 1849 Hungarian Republic crushed by Austria & Russia
- August 9, 1855 Battle of Acapulco during Mexican Liberal uprising
- August 9, 1877 Indian Wars: Battle of Big Hole – A small band of Nez Perc Indians clash with the United States Army.
- August 9, 1902 Edward VII is crowned king of the United Kingdom.
- August 9, 1907 The first Boy Scout encampment concludes at Brownsea Island in Southern England.
- August 9, 1918 “Cpl. Alexander P. Brereton (8th Cdn. Infantry Batt.) wins the Victoria Cross at Amiens, France”
- August 9, 1918 “Cpl. Frederick G. Coppins (8th Cdn. Infantry Batt.) wins the Victoria Cross at Amiens, France”
- August 9, 1918 “Cpl. Harry G. B. Miner (58th Cdn. Infantry Batt.) wins the Victoria Cross at Amiens, France”
- August 9, 1918 “Cpl. Joseph Kaeble (22nd Cdn. Infantry Batt.) wins the Victoria Cross at Amiens, France”
- August 9, 1918 “Lt. James E. Tait (78th Cdn. Infantry Batt.) wins the Victoria Cross at Amiens, France”
- August 9, 1918 “Lt. Jean Brillant (22nd Cdn. Infantry Batt.) wins the Victoria Cross at Amiens, France”
- August 9, 1918 “Sgt. Raphael Louis Zengel (5th Cdn. infanctry Batt.) wins the Victoria Cross at Amiens, France”
- August 9, 1930 Betty Boop debutes in Max Fleischer’s animated cartoon Dizzy Dishes
- August 9, 1936 Jesse Owens wins 4th gold medal of Berlin Olympics
- August 9, 1936 Summer Olympic Games: Games of the XI Olympiad: Jesse Owens wins his fourth gold medal at the games becoming the first American to win four medals in one Olympiad.
- August 9, 1942 “HMAS CANBERRA (RAN) sunk in the South West Pacific, SE of Savo Island off northern Guadalcanal, Solomon Islands – by torpedoes and 8in gunfire of Japanese cruiser force.”
- August 9, 1942 HMAS Canberra sunk in battle of Savo Island
- August 9, 1942 “Indian leader, Mahatma Gandhi is arrested in Bombay by British forces, launching the Quit India Movement.”
- August 9, 1944 The United States Forest Service and the Wartime Advertising Council release posters featuring Smokey Bear for the first time.
- August 9, 1945 “A second atomic bomb is dropped on Nagasaki; Soviets declare war on Japan, attacking Manchuria.”
- August 9, 1945 “Lt. Robert H. Gray (Royal Cdn. Naval Volunteer Reserve) wins the Victoria Cross at Onagawa BAy Honshu, Japan”
- August 9, 1945 “World War II: Nagasaki is devastated when an atomic bomb, “”Fat Man””, is dropped by the United States B-29 Bockscar. 70,000 people are killed instantly.”