In History, Today on March 21

Thomas Cranmer, the former Archbishop of Canterbury, was executed for heresy under the reign of Queen Mary I of England. His execution marked a significant moment in the Marian Persecutions, which aimed to restore Roman Catholicism in England.

The Battle of Heliopolis took place during the French Revolutionary Wars, where French forces under General Jean-Baptiste Kléber defeated the Ottoman army near Cairo, Egypt. This battle was part of the French campaign in Egypt and Syria.

The Napoleonic Code, a fundamental set of laws for France, was enacted. It served as a major influence on civil law codes worldwide.

The Bahá'í calendar, also known as the Badíʿ calendar, began. It is a solar calendar with 19 months of 19 days each, plus an additional period of 'Intercalary Days' to adjust to the solar year. This calendar is used by followers of the Bahá'í Faith.

Journalist Henry Morton Stanley began his famous expedition to find the missing explorer and missionary David Livingstone in Africa.

The German Spring Offensive, also known as the Kaiserschlacht, began during World War I. It was a series of German attacks along the Western Front, marking the last major German offensive of the war.

The Sharpeville massacre occurred in South Africa when police opened fire on a crowd of black protesters, killing 69 people. The protest was against the apartheid pass laws, and the event became a turning point in the struggle against apartheid.

Alcatraz Federal Penitentiary, located on Alcatraz Island in San Francisco Bay, was closed. The prison had been operational since 1934 and was known for housing some of America's most notorious criminals.

U.S. President Jimmy Carter announced a boycott of the 1980 Summer Olympics in Moscow in response to the Soviet invasion of Afghanistan. This decision led to a significant number of countries joining the boycott.

Namibia gained independence from South Africa, marking the end of a long struggle for freedom and the beginning of a new chapter as a sovereign nation.

The United States and coalition forces launched a ground invasion of Iraq, marking the beginning of the Iraq War.

Twitter was founded by Jack Dorsey, Noah Glass, Biz Stone, and Evan Williams, marking the beginning of a new era in social media communication.

The Syrian Civil War began with nationwide protests against President Bashar al-Assad's government, part of the wider wave of the Arab Spring.

The Syrian government launched a major offensive against opposition forces in the city of Homs, marking a significant escalation in the Syrian Civil War.

The European Space Agency launched the Planck satellite to study the Cosmic Microwave Background, providing insights into the early universe.

Russia formally annexed Crimea after a controversial referendum, escalating tensions with Ukraine and Western countries.

Kazakhstan's capital was renamed from Astana to Nur-Sultan in honor of the former president Nursultan Nazarbayev.