1215day.year
Zhongdu (now Beijing), then under the control of the Jurchen ruler Emperor Xuanzong of Jin, is captured by the Mongols under Genghis Khan, ending the Battle of Zhongdu.
Mongol forces under Genghis Khan capture Zhongdu (modern Beijing), ending a key siege during their northern China campaign.
On May 31, 1215, Mongol forces under the leadership of Genghis Khan laid siege to Zhongdu, the Jurchen capital.
Despite strong fortifications and fierce resistance, the city's defenses eventually succumbed to the relentless attackers.
The fall of Zhongdu, known today as Beijing, marked a decisive moment in the Mongol conquest of northern China.
Emperor Xuanzong of Jin was forced to abandon his seat of power, seeking refuge further south.
This victory opened the way for subsequent Mongol advances, reshaping the political landscape of the region.
The event demonstrated the strategic prowess of the Mongol war machine and its impact on East Asian history.
1215
Zhongdu
Jurchen
Emperor Xuanzong of Jin
Mongols
Genghis Khan
Battle of Zhongdu
1223day.year
Mongol invasion of the Cumans: Battle of the Kalka River: Mongol armies of Genghis Khan led by Subutai defeat Kievan Rus' and Cumans.
At the Battle of the Kalka River, Mongol armies commanded by Subutai defeat the combined forces of Kievan Rus' and the Cumans.
The Battle of the Kalka River took place on May 31, 1223, as Mongol scouting parties met the forces of Kievan Rus' and the Cumans.
Commanded by the famed general Subutai, the Mongol contingents employed sophisticated tactics to encircle their opponents.
Inferior coordination and unfamiliar tactics led the Rus' princes and their Cuman allies into a devastating trap.
The Mongols inflicted heavy casualties, forcing the survivors into a disastrous retreat across the frozen river.
The encounter served as a stark warning of Mongol military superiority to European realms.
It foreshadowed later invasions that would sweep across Eastern Europe in the following decades.
1223
Battle of the Kalka River
Mongol
Genghis Khan
Subutai
Kievan Rus'
Cumans
1293day.year
Mongols depart Java after the failed Mongol invasion against King Kertanegara of Singhasari.
After a failed invasion, Mongol forces withdraw from Java, marking the end of their campaign against Singhasari.
In 1293, Mongol forces concluded their ill-fated expedition against the kingdom of Singhasari in Java.
Dispatched by Kublai Khan to punish a defiant regional ruler, they initially captured the port of Tuban.
However, shifting alliances and local resistance under King Kertanegara thwarted Mongol ambitions.
Facing supply issues and potential ambush, the invaders decided to withdraw from the island.
Their departure marked the end of direct Mongol intervention in the Indonesian archipelago.
The episode influenced the rise of the Majapahit Empire, which succeeded Singhasari and shaped Javanese history.
1293
Mongols
Mongol invasion
Kertanegara
Singhasari
1805day.year
French and Spanish forces begin the assault against British forces occupying Diamond Rock, Martinique.
French and Spanish forces launch a coordinated naval assault to retake the strategically important Diamond Rock in Martinique from British occupation.
In the midst of the Napoleonic Wars, the French and Spanish navies aimed to dislodge British forces from the strategically located Diamond Rock off Martinique. Diamond Rock had been fortified and declared a British naval outpost to control regional shipping lanes. On May 31, 1805, a joint assault force began operations to retake the rock by bombarding shore batteries and landing troops. The operation involved specialized vessels and marine units trained for amphibious attacks. Although the initial phase achieved surprise, the rugged terrain and heavy fortifications posed challenges. The fall of Diamond Rock would restore French influence over the Caribbean waters. This engagement highlighted the global scale of the conflict between European powers.
1805
assault
Diamond Rock
1862day.year
American Civil War: Peninsula Campaign: Confederate forces under Joseph E. Johnston and G.W. Smith engage Union forces under George B. McClellan outside the Confederate capital of Richmond, Virginia.
Confederate and Union armies clash outside Richmond in the first major battle of the Civil War's Peninsula Campaign.
In the American Civil War's Peninsula Campaign, Confederate forces under General Joseph E. Johnston and General G.W. Smith confronted Major General George B. McClellan's Union army near Richmond. On May 31, 1862, the two armies engaged in a series of skirmishes and defensive actions outside the Confederate capital. The Confederates aimed to halt the Union advance down the Virginia Peninsula toward Richmond. McClellan's cautious tactics and strong defensive positions prolonged the engagement. Despite heavy artillery exchanges, neither side gained a decisive victory that day. The fighting foreshadowed a protracted siege that would define the campaign. The battle underscored the strategic importance of Richmond and set the stage for future Confederate counterattacks.
1862
American Civil War
Peninsula Campaign
Joseph E. Johnston
G.W. Smith
engage
George B. McClellan
Richmond, Virginia
1864day.year
American Civil War: Overland Campaign: Battle of Cold Harbor: The Army of Northern Virginia engages the Army of the Potomac.
Ulysses S. Grant's Army of the Potomac clashes with Robert E. Lee's Army of Northern Virginia at the Battle of Cold Harbor.
During Ulysses S. Grant's Overland Campaign, the Battle of Cold Harbor pitted the Army of Northern Virginia against the Army of the Potomac. On May 31, 1864, Union forces launched assaults on entrenched Confederate positions near Mechanicsville, Virginia. The well-fortified lines of Robert E. Lee's army inflicted severe casualties on repeated Federal attacks. Grant's aggressive tactics resulted in one of the war's highest casualty rates over a short period. The battle revealed the lethal effectiveness of defensive earthworks in Civil War combat. Following days of fighting, both armies remained near their original positions with little territorial change. Cold Harbor became emblematic of the brutal stalemate and high human cost of the conflict.
1864
Overland Campaign
Battle of Cold Harbor
Army of Northern Virginia
Army of the Potomac
1902day.year
Second Boer War: The Treaty of Vereeniging ends the war and ensures British control of South Africa.
The Treaty of Vereeniging is signed, formally ending the Second Boer War and confirming British control over South Africa.
The Treaty of Vereeniging was signed on May 31, 1902, ending the Second Boer War between the British Empire and the Boer republics of South Africa. Negotiated in Vereeniging, the treaty terms granted British sovereignty in exchange for amnesty and eventual self-government for Afrikaners. The conflict, which had seen guerrilla warfare and scorched-earth tactics, concluded after months of peace talks. British leaders, including Lord Milner, and Boer representatives, led by Jan Smuts and Louis Botha, crafted the final agreement. The treaty laid the groundwork for the creation of the Union of South Africa in 1910. Despite bitterness over British tactics, the settlement facilitated reconciliation and the integration of the Boer territories under colonial rule. The Vereeniging accord marked a turning point in South Africa's transition from divided republics to a unified dominion.
1902
Second Boer War
Treaty of Vereeniging
1911day.year
The President of Mexico Porfirio Díaz flees the country during the Mexican Revolution.
Mexican President Porfirio Díaz resigns and flees amid revolutionary uprisings, ending decades of authoritarian rule.
Facing escalating rebellion during the Mexican Revolution, long-time ruler Porfirio Díaz relinquished power and fled Mexico on May 31, 1911.
Díaz’s departure marked the collapse of a 35-year-long presidency characterized by modernization and political repression.
Revolutionary leaders, including Francisco Madero, had mobilized widespread support against Díaz’s centralized authority and electoral fraud.
Díaz's resignation opened the path for democratic reforms and social change, though Mexico would endure years of continued conflict.
His exile in France symbolized the end of an era and the beginning of a tumultuous chapter in Mexican history.
President of Mexico
Porfirio Díaz
Mexican Revolution
1916day.year
World War I: Battle of Jutland: The British Grand Fleet engages the High Seas Fleet in the largest naval battle of the war, which proves indecisive.
The Battle of Jutland, the largest naval engagement of World War I, ends without a decisive victor.
From May 31 to June 1, 1916, the British Royal Navy's Grand Fleet clashed with the German High Seas Fleet off the coast of Jutland in the North Sea.
Over 250 ships participated in what became the largest naval battle of World War I.
Though Germany inflicted heavier ship losses, the Royal Navy maintained its blockade of the Central Powers.
The engagement demonstrated the deadly power of modern battleships and revealed tactical and communication challenges.
While tactically inconclusive, the battle secured British naval dominance for the remainder of the war.
1916
World War I
Battle of Jutland
Grand Fleet
High Seas Fleet
1941day.year
Anglo-Iraqi War: The United Kingdom completes the re-occupation of Iraq and returns 'Abd al-Ilah to power as regent for Faisal II.
British forces re-occupy Iraq, reinstating 'Abd al-Ilah as regent amid World War II tensions.
On May 31, 1941, British troops secured the re-occupation of Iraq after defeating a pro-Axis coup led by Rashid Ali al-Gaylani.
The operation restored 'Abd al-Ilah as regent for the young King Faisal II and maintained British strategic interests in the Middle East.
Control of Iraqi oil fields and supply routes to British territories was crucial to the Allied war effort.
The swift campaign demonstrated the importance of regional alliances and air power in modern conflict.
This action marked a key moment in the broader struggle for influence in the Middle East during World War II.
1941
Anglo-Iraqi War
Iraq
'Abd al-Ilah
Faisal II
1942day.year
World War II: Imperial Japanese Navy midget submarines begin a series of attacks on Sydney, Australia.
Three Imperial Japanese Navy midget submarines launched a daring raid on Sydney Harbor during World War II, targeting Allied vessels and coastal defenses.
On the night of May 31, 1942, three Imperial Japanese Navy midget submarines launched a surprise raid on Sydney Harbor as part of World War II operations. Their aim was to strike Allied naval vessels and disrupt reinforcements bound for the Pacific front. One submarine managed to infiltrate the harbor defenses and fired torpedoes at moored ships, inadvertently sinking the ferry HMAS Kuttabul and causing significant casualties. The other two subs were forced to retreat and were later lost, with none of the crews returning home. This attack marked the only Axis naval offensive on the Australian mainland and prompted a comprehensive review of the nation’s coastal security. Its daring nature and tragic outcome have made it a defining moment in Australia’s wartime narrative.
1942
World War II
Imperial Japanese Navy
midget submarines
attacks on Sydney
1973day.year
The United States Senate votes to cut off funding for the bombing of Khmer Rouge targets within Cambodia, hastening the end of the Cambodian Civil War.
The U.S. Senate votes to end funding for the bombing of Khmer Rouge targets in Cambodia, accelerating the conclusion of the Cambodian Civil War.
On May 31, 1973, the United States Senate passed legislation to terminate military funding for bombing operations against Khmer Rouge positions within Cambodia. This decision stemmed from growing domestic opposition to the Vietnam War and concerns over expanding the conflict into neighboring countries. By cutting off financial support, senators aimed to curb U.S. involvement in Southeast Asia and pressure all parties toward a negotiated settlement. The vote significantly reduced aerial bombardment and hastened the collapse of the Lon Nol regime in Cambodia. Within months, the Khmer Rouge would seize control of Phnom Penh, reshaping the nation’s political landscape. The Senate’s action marked a pivotal shift in U.S. war policy and foreshadowed the broader withdrawal of American forces from Indochina.
1973
United States Senate
Khmer Rouge
Cambodia
Cambodian Civil War