On this day: 15 March

Roman consul Aulus Manlius Vulso celebrates an ovation for concluding the war against Veii and securing a forty years' truce.

The Roman Republic under its new consuls Publius Sulpicius Galba and Gaius Aurelius Cotta declares war on Philip V of Macedon, starting the Second Macedonian War.

Constantius Gallus is elevated as Caesar and then sent to Antioch to govern the Roman East.

Odoacer, the first barbarian King of Italy after the fall of the Western Roman Empire, is slain by Theoderic the Great, king of the Ostrogoths, while the two kings were feasting together.

Byzantine emperor Michael III overthrew the regency of his mother Theodora (pictured) to assume power for himself.

Al-Hadi ila'l-Haqq Yahya enters Sa'dah and founds the Zaydi Imamate of Yemen.

Reconquista: Portuguese troops under King Afonso I captured the city of Santarém from the Almoravids.

In the Battle of Halmyros, the Catalan Company defeated the forces of Walter V, Count of Brienne, taking control of the Duchy of Athens, a Crusader state in present-day Greece.

Mughal Emperor Akbar abolishes the jizya tax on non-Muslim subjects.

George Washington delivered a speech to Continental Army officers in Newburgh, New York, asking them to support the supremacy of the Congress of the Confederation, defusing a potential coup.

Maine is admitted as the twenty-third U.S. state.

American sailor Benjamin Morrell erroneously reported the existence of New South Greenland, a phantom island, near Antarctica.

A revolution breaks out in Hungary, and the Habsburg rulers are compelled to meet the demands of the reform party.

France and Vietnam signed the Second Treaty of Saigon, further recognizing the full sovereignty of France over Cochinchina.

John McCloskey, the Roman Catholic archbishop of New York, was created the first cardinal from the United States.

The first parliamentary elections of Finland (at the time the Grand Duchy of Finland) are held.

Prospectors drilled into a pressurized deposit within the Midway-Sunset Oil Field in California, resulting in the largest accidental oil spill in history, which eventually released 9 million barrels (1.4 million m3) of crude oil over 18 months.

Six days after Pancho Villa and his cross-border raiders attacked Columbus, New Mexico, U.S. general John J. Pershing led a punitive expedition into Mexico to pursue him.

Russian Revolution: Tsar Nicholas II was forced to abdicate in the February Revolution, ending three centuries of Romanov rule.

The American Legion is founded.

After Egypt gains nominal independence from the United Kingdom, Fuad I becomes King of Egypt.

Sing-Song Girl Red Peony (booklet pictured), one of the first sound films produced in China, was released in Shanghai.

Germany occupies Czechoslovakia.

Carpatho-Ukraine declares itself an independent republic, but is annexed by Hungary the next day.

World War II: German forces recaptured Kharkov after four days of house-to-house fighting against Soviet troops, ending the month-long Third Battle of Kharkov.

The Iranian oil industry was nationalized in a movement led by Mohammad Mosaddegh.

The musical My Fair Lady, based on George Bernard Shaw's play Pygmalion, debuted at the Mark Hellinger Theatre in New York City.

Students from the Atlanta University Center, inspired by similar actions in Greensboro, North Carolina, began occupying lunch counters in Atlanta, Georgia.

At the 1961 Commonwealth Prime Ministers' Conference, South Africa announces that it will withdraw from the Commonwealth when the South African Constitution of 1961 comes into effect.

President Lyndon B. Johnson, responding to the Selma crisis, tells the U.S. Congress "We shall overcome" while advocating the Voting Rights Act.

Somalia and Ethiopia sign a truce to end the Ethio-Somali War.

Mikhail Gorbachev is elected as the first and only President of the Soviet Union.

Cold War: The Treaty on the Final Settlement with Respect to Germany comes into effect, granting full sovereignty to the Federal Republic of Germany.

Beginning of the Syrian revolution.

Beginning of the 2019–20 Hong Kong protests.

Approximately 1.4 million young people in 123 countries go on strike to protest climate change.

The 2022 Sri Lankan protests begins amidst Sri Lanka's economic collapse.