May 21 in History

Diocletian, nicknamed Jovius, was Roman emperor from 284 until his abdication in 305. He was born Diocles to a family of low status in the Roman province of Dalmatia. As with other Illyrian soldiers of the period, Diocles rose through the ranks of the military early in his career, serving under Aurelian and Probus, and eventually becoming a cavalry commander for the army of Emperor Carus. After the deaths of Carus and his son Numerian on a campaign in Persia, Diocles was proclaimed emperor by the troops, taking the name "Diocletianus". The title was also claimed by Carus's surviving son, Carinus, but Diocletian defeated him in the Battle of the Margus.

Pope John VIII was the bishop of Rome and ruler of the Papal States from 14 December 872 to his death. He is often considered one of the most able popes of the 9th century.

Michael IX Palaiologos or Palaeologus was Byzantine emperor together with his father, Andronikos II Palaiologos, from 1294 until his death. Andronikos II and Michael IX ruled as equal co-rulers, both using the title autokrator.

Dušan's Code is a compilation of several legal systems that was enacted by Stefan Uroš IV Dušan of Serbia in 1349. It drew upon Roman law, Byzantine law, as well as elements of customary and canon law. It was used in the Serbian Empire and the succeeding Serbian Despotate. It is considered an early constitution, or close to it; an advanced set of laws which regulated all aspects of life such as family relations, property rights, contracts, and crimes.

James I was King of Scots from 1406 to 1437. The youngest of three sons, he was born in Dunfermline Abbey to King Robert III and his wife Annabella Drummond. His older brother David, Duke of Rothesay died under suspicious circumstances while being detained by their uncle, Robert, Duke of Albany. His other brother, Robert, died young. Fears for James's safety grew through the winter of 1405/6 and plans were made to send him to France. In February 1406, James was forced to take refuge in the castle of the Bass Rock in the Firth of Forth after his escort was attacked by supporters of Archibald, 4th Earl of Douglas. He remained there until mid-March, when he boarded a vessel bound for France. On 22 March, English pirates captured the ship and delivered the prince to Henry IV of England. The ailing Robert III died on 4 April, and the 11-year-old James, now the uncrowned King of Scotland, would not regain his freedom for another eighteen years.

The Concert of The Hague, signed on 21 May 1659, was an outline of the common stance of England, France and the Dutch Republic regarding the Second Northern War. The powers agreed that the Swedish Empire and Denmark–Norway should settle for a peace treaty based on the Treaty of Roskilde, including free navigation through The Sound and the Baltic Sea based on the Treaty of Elbing. The subsequent Dano-Swedish Peace of Copenhagen largely followed the terms dictated by the Concert of the Hague.

The szlachta were the hereditary noble estate in the Kingdom of Poland, the Grand Duchy of Lithuania, and the Polish–Lithuanian Commonwealth. It was the dominating social class in the Kingdom of Poland and the Commonwealth, which was exercising political rights and power. Szlachta as a class differed substantially from the feudal nobility of Western Europe. The estate was officially abolished in 1921 by the March Constitution.

The Imperial Order of Saint Alexander Nevsky was an order of chivalry of the Russian Empire first awarded on 1 June [O.S. 21 May] 1725 by Empress Catherine I of Russia.

In volcanology, a lava dome is a circular, mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions on Earth form lava domes. The geochemistry of lava domes can vary from basalt to rhyolite although the majority are of intermediate composition. The characteristic dome shape is attributed to high viscosity that prevents the lava from flowing very far. This high viscosity can be obtained in two ways: by high levels of silica in the magma, or by degassing of fluid magma. Since viscous basaltic and andesitic domes weather fast and easily break apart by further input of fluid lava, most of the preserved domes have high silica content and consist of rhyolite or dacite.

In the Battle of Aspern–Essling, Napoleon crossed the Danube near Vienna, but the French and their allies were attacked and forced back across the river by the Austrians under Archduke Charles. It was the first time Napoleon had been personally defeated in a major battle, as well as his first battle defeat in 10 years since the siege of Acre, and his first battle defeat as head of state, although he did suffer a tactical defeat in the Battle of Caldiero and in the Second Battle of Bassano. Archduke Charles drove out the French but fell short of destroying their army. The French lost over 20,000 men, including one of Napoleon's ablest field commanders and closest friends, Marshal Jean Lannes.

The American Civil War was a civil war in the United States between the Union and the Confederacy, which was formed in 1861 by states that had seceded from the Union to preserve slavery in the United States. The South saw slavery as threatened because of the election of Abraham Lincoln and the growing abolitionist movement in the North. The war ended with Union victory, the dissolution of the Confederacy and the abolition of slavery, freeing four million African Americans.

The Battle of Spotsylvania Court House, sometimes more simply referred to as the Battle of Spotsylvania, was the second major battle in Lt. Gen. Ulysses S. Grant and Maj. Gen. George G. Meade's 1864 Overland Campaign of the American Civil War. Following the bloody but inconclusive Battle of the Wilderness, Grant's army disengaged from Confederate General Robert E. Lee's army and moved to the southeast, attempting to lure Lee into battle under more favorable conditions. Elements of Lee's army beat the Union army to the critical crossroads of the Spotsylvania Court House in Spotsylvania County, Virginia, and began entrenching. Fighting occurred on and off from May 8 through May 21, 1864, as Grant tried various schemes to break the Confederate line. In the end, the battle was tactically inconclusive, but both sides declared victory. The Confederacy declared victory because they were able to hold their defenses. The United States declared victory because the Federal offensive continued and Lee's army suffered losses that could not be replaced. With almost 32,000 casualties on both sides, Spotsylvania was the costliest battle of the campaign.

The Paris Commune was a French revolutionary government that seized power in Paris on 18 March 1871 and controlled parts of the city until 28 May 1871. During the Franco-Prussian War of 1870–1871, the French National Guard had defended Paris, and working class radicalism grew among its soldiers. Following the establishment of the French Third Republic in September 1870 and the complete defeat of the French Army by the Germans by March 1871, soldiers of the National Guard seized control of the city on 18 March. The Communards killed two French Army generals and refused to accept the authority of the Third Republic; instead, the radicals set about establishing their own independent government.

The War of the Pacific, also known by multiple other names, was a war between Chile and a Bolivian–Peruvian alliance from 1879 to 1884. Fought over Chilean claims on coastal Bolivian territory in the Atacama Desert, the war ended with victory for Chile, which gained a significant amount of resource-rich territory from Peru and Bolivia. The war demonstrated Chile's military-technological superiority over its opponents at the time.

The Manchester Ship Canal is a 36-mile-long (58 km) inland waterway in North West England that links Manchester to the Irish Sea. Beginning in the Mersey estuary at Eastham, near Ellesmere Port in Cheshire, it generally follows the original routes of the rivers Mersey and Irwell through the historic counties of Cheshire and Lancashire before terminating to the east of Salford Quays near Pomona Docks and a junction with the Bridgewater Canal where it meets the Irwell. Several sets of locks lift vessels about 60 ft (18 m) to the canal's terminus in Manchester. Landmarks along its route include the Barton Swing Aqueduct – the world's only swing aqueduct – and Trafford Park, the world's first planned industrial estate and one of the largest in Europe.

The president of Mexico, officially the president of the United Mexican States, is the head of state and head of government of Mexico. Under the Constitution of Mexico, the president heads the executive branch of the federal government and is the commander in chief of the Mexican Armed Forces.

The Great Atlanta Fire of 1917 began just after noon on 21 May 1917 in the Old Fourth Ward of Atlanta, Georgia. It is unclear just how the fire started, but it was fueled by hot temperatures and strong winds which propelled the fire. The fire, which burned for nearly 10 hours, destroyed 300 acres (120 ha) and 1,900 structures displacing over 10,000 people. Damages were estimated at $5 million,.

Doktor Faust is an opera by Ferruccio Busoni with a German libretto by the composer, based on the myth of Faust. Busoni worked on the opera, which he intended as his masterpiece, between 1916 and 1924, but it was still incomplete at the time of his death. His pupil Philipp Jarnach finished it. More recently, in 1982, Antony Beaumont completed the opera using sketches by Busoni that were previously thought to have been lost. Nancy Chamness published an analysis of the libretto to Doktor Faust and a comparison with Goethe's version.

Amelia Mary Earhart was an American aviator and aviation pioneer who became one of the most celebrated figures of early flight.

Sada Abe was a Japanese geisha and prostitute who murdered her lover, Kichizō Ishida , via strangulation on May 18, 1936, before cutting off his penis and testicles and carrying them around with her in her kimono. The story became a national sensation in Japan, acquiring mythic overtones; it has also been interpreted by artists, philosophers, novelists and filmmakers. Abe was released after serving five years in prison and went on to write an autobiography.

The National War Memorial, titled The Response, is a tall, granite memorial arch with accreted bronze sculptures in Ottawa, Ontario, designed by Vernon March and first dedicated by King George VI in 1939. Originally built to commemorate the Canadians who died in the First World War, it was in 1982 rededicated to also include those killed in the Second World War and Korean War and again in 2014 to add the dead from the Second Boer War and War in Afghanistan, as well as all Canadians killed in all conflicts past and future. It now serves as the pre-eminent war memorial of 76 cenotaphs in Canada. In 2000, the Tomb of the Unknown Soldier was added in front of the memorial and symbolizes the sacrifices made by all Canadians who have died or may yet die for their country.

The 9th Street Art Exhibition of Paintings and Sculpture is the official title artist Franz Kline hand-lettered onto the poster he designed for the Ninth Street Show. Now considered historic, the artist-led exhibition marked the formal debut of Abstract Expressionism, and the first American art movement with international influence. The School of Paris, long the headquarters of the global art market, typically launched new movements, so there was both financial and cultural fall-out when all the excitement was suddenly emanating from New York. The postwar New York avant-garde, artists like Willem de Kooning and Jackson Pollock, would soon become "art stars," commanding large sums and international attention. The Ninth Street Show marked their "stepping-out," and that of nearly 75 other artists, including Harry Jackson, Helen Frankenthaler, Michael Goldberg, Joan Mitchell, Grace Hartigan, Robert De Niro Sr., John Ferren, Philip Guston, Elaine de Kooning, Louis Schanker, Lee Krasner, Franz Kline, Ad Reinhardt, Ludwig Sander, David Smith, Milton Resnick, Joop Sanders, Robert Motherwell, Barnett Newman, and many others who were then mostly unknown to an art establishment that ignored experimental art without a ready market.

The Ulster Volunteer Force (UVF) is an Ulster loyalist paramilitary group based in Northern Ireland. Formed in 1965, it first emerged in 1966. Its first leader was Gusty Spence, a former British Army soldier from Northern Ireland. The group undertook an armed campaign of almost thirty years during The Troubles. It declared a ceasefire in 1994 and officially ended its campaign in 2007, although some of its members have continued to engage in violence and criminal activities. The group is a proscribed organisation and is on the terrorist organisation list of the United Kingdom.

Michelangelo di Lodovico Buonarroti Simoni, known mononymously as Michelangelo, was an Italian sculptor, painter, architect, and poet of the High Renaissance. He was born in the Republic of Florence but was mostly active in Rome from his 30s onwards. His work was inspired by models from classical antiquity and had a lasting influence on Western art. Michelangelo's creative abilities and mastery in a range of artistic arenas define him as an archetypal Renaissance man, along with his rival and elder contemporary, Leonardo da Vinci. Given the sheer volume of surviving correspondence, sketches, and reminiscences, Michelangelo is one of the best-documented artists of the 16th century. He was lauded by contemporary biographers as the most accomplished artist of his era.

The White Night riots were a series of violent events sparked by an announcement of a lenient sentencing of Dan White for the assassinations of George Moscone, the mayor of San Francisco, and of Harvey Milk, a member of the city's Board of Supervisors who was one of the first openly gay elected officials in the United States. The events took place on the night of May 21, 1979, in San Francisco. Earlier that day White had been convicted of voluntary manslaughter, the lightest possible conviction for his actions. The lesser conviction outraged the city's gay community, setting off the most violent reaction by gay Americans since the 1969 Stonewall riots in New York City.

Transamerica Corporation is an American holding company for various life insurance companies and investment firms operating primarily in the United States, offering life and supplemental health insurance, investments, and retirement services. The company is located in Baltimore, Maryland, with its subsidiary Transamerica Life Company headquartered in Cedar Rapids, Iowa; It has back offices Denver, Colorado; Harrison, New York; Toronto, Ontario; Philadelphia, Pennsylvania; and Knoxville, Tennessee. Additional affiliated offices are located throughout the United States. In 1999, it became an independent subsidiary of multinational company Aegon.

Margaret Hilda Thatcher, Baroness Thatcher was a British stateswoman who served as Prime Minister of the United Kingdom from 1979 to 1990 and Leader of the Conservative Party from 1975 to 1990. She was the longest-serving British prime minister of the 20th century and the first woman to hold the office. As prime minister, she implemented policies that came to be known as Thatcherism. A Soviet journalist dubbed her the "Iron Lady", a nickname that became associated with her uncompromising politics and leadership style.

Mengistu Haile Mariam is an Ethiopian communist revolutionary, military officer, and former statesman who served as the head of state of Ethiopia from 1977 to 1991. He was General Secretary of the Workers' Party of Ethiopia from 1984 to 1991, chairman of the Derg—the Marxist–Leninist military junta that ruled Ethiopia—from 1977 to 1987, and president of the People's Democratic Republic of Ethiopia (PDRE) from 1987 to 1991.

The Democratic Republic of Yemen, was a short-lived state that fought against the mainland Yemen in the 1994 Yemeni Civil War. It was declared in May 1994 and covered all of the former South Yemen.

The Trappists, officially known as the Order of Cistercians of the Strict Observance and originally named the Order of Reformed Cistercians of Our Lady of La Trappe, are a Catholic religious order of cloistered monastics that branched off from the Cistercians. They follow the Rule of Saint Benedict and have communities of both monks and nuns that are known as Trappists and Trappistines, respectively. They are named after La Trappe Abbey, the monastery from which the movement and religious order originated. The movement began with the reforms that Abbot Armand Jean le Bouthillier de Rancé introduced in 1664, later leading to the creation of Trappist congregations, and eventually the formal constitution as a separate religious order in 1892.

Suharto was an Indonesian general and politician who served as the second and longest-serving president of Indonesia from 1967 to 1998.

Christiane Marie Taubira is a French politician who served as Minister of Justice of France in the governments of Prime Ministers Jean-Marc Ayrault and Manuel Valls under President François Hollande from 2012 until 2016. She was a member of the National Assembly of France for French Guiana from 1993 to 2012 and member of the European Parliament from 1994 to 1999.

A roller coaster is a type of amusement ride employing a form of elevated railroad track that carries passengers on a train through tight turns, steep slopes, and other elements. Roller coasters are usually designed to produce a thrilling experience, though some roller coasters aim to provide a more gentle experience. Trains consist of open cars connected in a single line, and tracks are typically built and designed as a complete circuit in which trains depart from and return to the same loading station. The rides are typically found in amusement parks around the world but can also be located in shopping malls and zoos. The Roller Coaster DataBase records over 6,000 extant roller coasters as of January 2026.

The Japan Aerospace Exploration Agency (JAXA) is the operator of the Japanese space program and Japan's national aeronautics research agency. It was formed in 2003 through the merger of the Institute of Space and Astronautical Science, the National Aerospace Laboratory of Japan, and the National Space Development Agency of Japan.

The Qafa e Vishës bus accident occurred on 21 May 2012, at Qafa e Vishës near Himarë, Albania, when a bus plunged 80 metres (260 ft) off a cliff. Most of the victims were students of Aleksandër Xhuvani University of Elbasan. The driver is also believed to have been killed. The students were travelling from Elbasan to Sarandë.

On 21 May 2014, a Taiwanese man carried out a stabbing spree targeting random civilians on a Taipei Metro C321 train near Jiangzicui Station, resulting in four deaths and 24 injuries. It was the first fatal attack on the city's subway system since operations began in 1996. The attacker, 21-year-old Cheng Chieh, was arrested after the attack. He was sentenced to death, in addition to 144 years in prison, and was executed on 10 May 2016.

On the afternoon of May 21, 2024, a violent and destructive EF4 tornado tracked across southwestern Iowa, United States, devastating the city of Greenfield. The tornado, known most commonly as the Greenfield tornado, destroyed many buildings and wind turbines across its path that stretched through Page, Taylor, Adams, and Adair counties, while also causing more than $31 million in property damage, killing five people and injuring 35 more. The tornado reached peak intensity within Greenfield, where National Weather Service surveyors denoted maximum wind speeds estimated at 185 mph (298 km/h), or EF4 on the Enhanced Fujita scale. However, estimated winds of 309–318 mph (497–512 km/h) were briefly determined from inside the tornado by a Doppler on Wheels portable radar unit, one of only three times that wind speeds exceeding 300 miles per hour (480 km/h) have been determined in a tornado from radar observations.