In History, Today on May 20

The ceasefire agreement between Israel and Hamas took effect, ending 11 days of intense conflict in the Gaza Strip.

Cyclone Amphan makes landfall in Eastern India and Bangladesh, causing extensive damage and leading to the evacuation of millions of people.

The International System of Units (SI) undergoes a major revision, redefining the kilogram, ampere, kelvin, and mole based on fundamental physical constants.

The Egyptian government declared a state of emergency after the EgyptAir Flight 804, traveling from Paris to Cairo, disappeared from radar over the Mediterranean Sea. Wreckage was later found and all 66 people on board were confirmed dead.

David Cameron's newly elected Conservative government delivered the Queen's Speech, outlining its legislative agenda, including plans for a referendum on UK membership of the European Union.

A massive tornado strikes Moore, Oklahoma, causing widespread destruction and resulting in 24 fatalities.

The first-ever legal same-sex marriages in Latin America were performed in Argentina, marking a significant milestone in LGBTQ+ rights in the region.

The Republic of Montenegro holds a referendum on independence from the State Union of Serbia and Montenegro, with a majority voting in favor.

East Timor becomes the first new sovereign state of the 21st century, regaining independence from Indonesia.

The discovery of the HIV virus that causes AIDS was published in the journal Science by Luc Montagnier and his team at the Pasteur Institute in France.

The Battle of Hamburger Hill during the Vietnam War ended after ten days of intense fighting, with U.S. and South Vietnamese forces capturing the heavily fortified hill from North Vietnamese troops.

The first prisoners arrived at the Auschwitz concentration camp in German-occupied Poland, marking the beginning of one of the most infamous sites of the Holocaust.

Amelia Earhart took off from Newfoundland, Canada, on her solo flight across the Atlantic Ocean, becoming the first woman to achieve this feat.

Charles Lindbergh took off from Roosevelt Field in New York, beginning the first solo nonstop transatlantic flight, which he completed the next day in Paris.

The United States passes the Cuba Amendment to end military occupation of Cuba, positioning it for independence as a U.S. protectorate, which effectively leads to the establishment of the Republic of Cuba two years later.

The eruption of Krakatoa began, leading to one of the most violent volcanic events in recorded history, which would culminate in August with massive loss of life and global climatic effects.

The Triple Alliance was formed between Germany, Austria-Hungary, and Italy, a military agreement that played a significant role in the prelude to World War I.

Levi Strauss and Jacob Davis received a U.S. patent for blue jeans with copper rivets, marking the birth of the iconic American garment.

President Abraham Lincoln signed the Homestead Act into law, which provided 160 acres of public land to settlers for a small fee, encouraging westward expansion in the United States.

The HMS Erebus and HMS Terror set sail from England on an ill-fated expedition to the Arctic under Captain Sir John Franklin, searching for the Northwest Passage.

York Minster, one of the largest Gothic cathedrals in Northern Europe, suffers its second major fire.

Napoleon Bonaparte reinstated slavery in the French colonies, reversing its abolition during the French Revolution.

A transit of Venus was observed by Jerimiah Dixon and Charles Mason at the Royal Observatory, Cape of Good Hope, which was part of efforts to measure the distance from Earth to the sun.

In the Battle of Naseby, a key engagement during the English Civil War, the Royalist forces suffered a significant defeat by the Parliamentarian army.

Thomas Thorpe published Shakespeare's sonnets in London, which included 154 sonnets, many of which are considered among the greatest in the English language.

Hernán Cortés, the Spanish Conquistador, entered Tenochtitlan, the capital of the Aztec Empire, to challenge the authority of the governor sent by Spain to arrest him.

Portuguese explorer Vasco da Gama arrived at Calicut (now Kozhikode), India, becoming the first European to reach India by sea, marking a significant milestone in the Age of Discovery.

Cola di Rienzo was acclaimed as the tribune of Rome, initiating a brief popular regime focused on restoring the grandeur of ancient Rome. Rienzo's assumption of power represented an effort to bridge the gap between the city's republican past and papal present.

The Kamakura earthquake occurred, which led to significant destruction and loss of life in the Kamakura region of Japan. This earthquake is estimated to have been a magnitude of around 7.1, causing fires and tsunamis that contributed to widespread damage.

The Battle of Dun Nechtain (also known as the Battle of Nechtansmere) took place. It was a pivotal battle where the Picts, under the leadership of King Bridei III, defeated the Northumbrians led by King Ecgfrith. This battle significantly curtailed Northumbrian expansion and secured Pictish independence from Northumbrian dominance.

The First Council of Nicaea was convened by the Roman Emperor Constantine I. This was the first ecumenical council of the Christian Church, held in the city of Nicaea (now İznik, Turkey). The council aimed to address the Arian controversy and resulted in the first uniform Christian doctrine, the Nicene Creed.