537day.year
Siege of Rome: The Byzantine general Belisarius receives his promised reinforcements, 1,600 cavalry, mostly of Hunnic or Slavic origin and expert bowmen. Despite shortages, he starts raids against the Gothic camps and Vitiges but is forced into a stalemate.
During the Gothic War, Belisarius received fresh Hunnic and Slavic cavalry reinforcements at the Siege of Rome in 537 AD, yet the stalemate with the Goths persisted.
In 537 AD, Belisarius led Byzantine forces in defending Rome against the Ostrogothic siege during Justinian’s Gothic War. On April 9, he finally received the 1,600-strong cavalry contingent, composed largely of skilled Hunnic and Slavic archers. Bolstered by these reinforcements, Belisarius conducted daring raids on enemy encampments and challenged the Gothic king Vitiges. Despite his tactical ingenuity, shortages of supplies and manpower prevented a decisive victory, resulting in a protracted stalemate. The siege exemplified the complex interplay of diplomacy, strategy, and multicultural forces in Justinian’s campaign to reconquer the Western Empire.
537
Siege of Rome
Belisarius
Hunnic
Slavic
bowmen
Gothic
Vitiges
1241day.year
Battle of Liegnitz: Mongol forces defeat the Polish and German armies.
In 1241, Mongol forces inflicted a crushing defeat on a Polish-German coalition at the Battle of Liegnitz, showcasing their superior tactics in Europe.
In April 1241, a Mongol army under General Subutai engaged a coalition of Polish knights and German forces near Liegnitz (present-day Legnica, Poland). The European knights were taken by surprise by the Mongols’ feigned retreats and devastating light cavalry tactics. Despite fierce resistance, the heavy cavalry charges of the crusader knights could not withstand the mobile Mongol archers and coordinated assaults. The crushing victory opened Central Europe to further Mongol incursions and instilled widespread fear among the region’s rulers. Although the Mongols withdrew soon after due to internal succession issues, the battle demonstrated the effectiveness of steppe warfare against medieval armies.
1241
Battle of Liegnitz
Mongol
1288day.year
Mongol invasions of Vietnam: Yuan forces are defeated by Trần forces in the Battle of Bach Dang in present-day northern Vietnam.
During the Mongol invasions of Vietnam in 1288, Trần dynasty forces achieved a decisive naval victory at the Battle of Bach Dang River.
In March–April 1288, the Yuan dynasty fleet attempted to invade Đại Việt via the Bach Dang river under Kublai Khan’s mandate. Trần Hưng Đạo, the Vietnamese commander, ordered steel-tipped wooden stakes planted in the riverbed and timed a counterattack with the ebbing tide. As the Yuan ships grew trapped, Vietnamese warships launched volleys of fire arrows and close combat assaults. The destruction of the Mongol fleet forced Kublai Khan to end his third invasion and solidified the Trần dynasty’s sovereignty. This battle remains celebrated in Vietnam for its ingenious use of terrain and popular resistance against a dominant empire.
1288
Mongol invasions of Vietnam
Yuan
Trần
Battle of Bach Dang
1388day.year
Despite being outnumbered 16:1, forces of the Old Swiss Confederacy are victorious over the Archduchy of Austria in the Battle of Näfels.
On April 9, 1388, the Old Swiss Confederacy secured a surprising victory against the Archduchy of Austria at the Battle of Näfels.
In the spring of 1388, Austrian forces launched an offensive to subjugate the cantons of Glarus, a member of the Old Swiss Confederacy. At Näfels in eastern Switzerland, the Swiss defenders, though outnumbered sixteen to one, used their knowledge of the mountainous terrain to set ambushes and defensive positions. Under the leadership of local commanders, they repelled multiple cavalry charges and exploited narrow passes to neutralize enemy advantages. The stunning Swiss victory not only lifted the siege of Glarus but also led to the Peace Treaty of Vienna in 1389, affirming the confederation’s independence. Näfels became a symbol of Swiss courage and solidarity in the face of overwhelming odds.
1388
Old Swiss Confederacy
Archduchy of Austria
Battle of Näfels
1511day.year
Resettled Shiite Muslims rise up in the Şahkulu rebellion under the leadership of Şahkulu against the Ottoman Empire.
In 1511, Shiite Muslims in Anatolia rebelled under Şahkulu’s leadership, challenging the Sunni authority of the Ottoman Empire.
In April 1511, discontented Shiite communities in Anatolia rallied under the leadership of Şahkulu, a Turkmen agitator claiming divine support. The rebels targeted Ottoman tax collectors and symbols of Sunni authority, seizing several towns and drawing followers from disenfranchised Turkmen tribes. Sultan Bayezid II responded by dispatching a large army to confront the insurgency, culminating in the rebels’ defeat at the hands of experienced Janissary forces. Although Şahkulu himself was killed in battle, the uprising exposed underlying sectarian tensions that would later influence the Safavid–Ottoman rivalry. The rebellion foreshadowed the role of religious identity in shaping early 16th-century Ottoman politics.
1511
Şahkulu rebellion
Şahkulu
Ottoman Empire
1609day.year
Eighty Years' War: Spain and the Dutch Republic sign the Treaty of Antwerp to initiate twelve years of truce.
In 1609, Spain and the Dutch Republic signed the Twelve Years’ Truce with the Treaty of Antwerp, pausing hostilities during the Eighty Years’ War.
By April 1609, three decades of brutal conflict between Habsburg Spain and the Dutch Republic had ravaged the Low Countries. Negotiators convened in Antwerp to broker a temporary truce, culminating in the Twelve Years’ Truce signed on April 9, 1609. The agreement recognized de facto independence for the Dutch, allowing for normalized trade and the exchange of prisoners. This pause in hostilities fostered economic recovery and allowed the Dutch Golden Age to flourish in the early 17th century. Though hostilities resumed in 1621, the truce shaped the political landscape of Northwest Europe for generations.
1609
Eighty Years' War
Spain
Dutch Republic
Treaty of Antwerp
1865day.year
American Civil War: Robert E. Lee surrenders the Army of Northern Virginia (26,765 troops) to Ulysses S. Grant at Appomattox Court House, Virginia, effectively ending the war.
Confederate General Robert E. Lee surrenders to Ulysses S. Grant at Appomattox, effectively ending the American Civil War.
On April 9, 1865, Confederate General Robert E. Lee met Union General Ulysses S. Grant at Appomattox Court House in Virginia to surrender the Army of Northern Virginia. Lee's 26,765 troops laid down their arms, signaling the collapse of the Confederacy. Grant offered generous terms, allowing soldiers to return home with their horses and sidearms. The surrender effectively ended the four-year Civil War that had divided the nation over slavery and secession. News of the agreement spread quickly, prompting further surrenders across Confederate forces. The meeting at Appomattox became a symbol of reconciliation and set the stage for Reconstruction. It remains one of the most significant moments in American history.
1865
American Civil War
Robert E. Lee
surrenders
Army of Northern Virginia
Ulysses S. Grant
Appomattox Court House, Virginia
1917day.year
World War I: The Battle of Arras: The battle begins with Canadian Corps executing a massive assault on Vimy Ridge.
The Battle of Arras begins as Canadian forces launch a major assault on Vimy Ridge during World War I.
On April 9, 1917, the Canadian Corps led a meticulously planned assault on German positions at Vimy Ridge near Arras, France. Supported by extensive artillery bombardments and innovative creeping barrages, the Canadians achieved a pivotal breakthrough. The victory marked the first time all four divisions of the corps fought together, showcasing exceptional coordination and engineering. Canadian tunneling units also played a critical role by undermining German defenses. The success at Vimy Ridge boosted Allied morale and demonstrated the effectiveness of combined arms tactics. It earned the Canadian forces an enduring reputation for military skill and is celebrated as a defining moment in Canada’s national history. The battle influenced subsequent offensives on the Western Front.
1917
World War I
Battle of Arras
Canadian Corps
massive assault on Vimy Ridge
1918day.year
World War I: The Battle of the Lys: The Portuguese Expeditionary Corps is crushed by the German forces during what is called the Spring Offensive on the Belgian region of Flanders.
German forces crush the Portuguese Expeditionary Corps at the Battle of the Lys during the WWI Spring Offensive.
During the German Spring Offensive on April 9, 1918, the Battle of the Lys unfolded in the Flanders region of Belgium. German divisions launched a powerful attack that overwhelmed the Portuguese Expeditionary Corps. Poorly supported and outnumbered, the Portuguese troops suffered heavy casualties and were forced into retreat. The breakthrough allowed German forces to advance toward key logistical hubs. Allied command struggled to reinforce the battered line amid challenging terrain and weather. The engagement underscored the risks of deploying underprepared units in critical sectors. It contributed to calls for reorganization within the Allied forces and highlighted the grueling nature of trench warfare.
1918
Battle of the Lys
Portuguese Expeditionary Corps
Spring Offensive
Flanders
1940day.year
World War II: Operation Weserübung: Germany invades Denmark and Norway.
Nazi Germany launches Operation Weserübung, invading Denmark and Norway at the start of World War II.
On April 9, 1940, Germany executed Operation Weserübung, simultaneously invading Denmark and Norway during World War II. The swift strikes aimed to secure strategic ports and iron ore routes critical to the German war effort. Denmark capitulated within hours, while Norwegian forces resisted in a series of battles. Allied attempts to intervene were hampered by logistical challenges and German aerial supremacy. The occupation of both countries provided Germany with vital naval bases and raw materials. The campaign demonstrated the effectiveness of Blitzkrieg tactics in northern Europe. It reshaped the balance of power in the region and set the stage for subsequent German operations in the North Atlantic.
1940
World War II
Operation Weserübung
Germany
Denmark
Norway
1942day.year
World War II: The Battle of Bataan ends and the Bataan Death March begins.
The surrender of U.S. and Filipino forces at Bataan triggers the brutal Bataan Death March.
On April 9, 1942, American and Filipino defenders in the Philippines capitulated after a grueling siege, marking the end of the Battle of Bataan.
Approximately 75,000 prisoners of war were forced to march over 60 miles in harrowing conditions with little food, water, or medical care.
Thousands perished along the route as Japanese captors applied extreme brutality and neglect.
The ordeal became a symbol of wartime atrocity and galvanized international outrage against the Japanese military.
Survivor testimonies later fueled war crimes trials and ensured the march's place in collective memory.
1942
Battle of Bataan
Bataan Death March
1942day.year
World War II: An Indian Ocean raid by Japan's 1st Air Fleet sinks the British aircraft carrier HMS Hermes and the Australian destroyer HMAS Vampire.
Japanese carrier aircraft in the Indian Ocean raid sink HMS Hermes and HMAS Vampire.
During the Indian Ocean raid of April 1942, Imperial Japanese Navy aircraft launched a surprise strike on Allied naval forces off the coast of Ceylon.
On April 9, torpedo bombers and dive bombers from Japan's 1st Air Fleet attacked and sank the British aircraft carrier HMS Hermes and the Australian destroyer HMAS Vampire.
The operation demonstrated Japan's growing naval air power and extended its reach into the Indian Ocean.
Allied forces suffered significant losses and were forced to reposition their ships to safer waters.
The raid underscored the strategic threat to British supply lines and fueled efforts to bolster anti-aircraft defenses in the region.
Indian Ocean raid
1st Air Fleet
HMS Hermes
HMAS Vampire