1914 Franz Ferdinand, Archduke of Austria and his wife Sophie are assassinated in Sarajevo by young Serbian nationalist Gavrilo Princip, the ''casus belli'' of World War I.
1914 World War I: Austria-Hungary declares war on Serbia after Serbia rejects the conditions of an ultimatum sent by Austria on July 23 following the assassination of Archduke Francis Ferdinand.
1914 Germany declares war on Russia at the opening of World War I. The Swiss Army mobilises because of World War I
1914 Germany declares war on Russia at the opening of World War I. The Swiss Army mobilises because of World War I
1914 World War I: Germany declares war against France.
1914 World War I: Germany invades Belgium. In response, the United Kingdom declares war on Germany. The United States declare their neutrality.
1914 World War I: the German minelayer ''Königin Luise'' lays a minefield about 40 miles of the Thames Estuary (Lowestoft). She is intercepted and sunk by the British light-cruiser ''HMS Amphion''.
1914 World War I: irst Battle of the Atlantic
1914 World War I: the United Kingdom declares war on Austria-Hungary; the countries of the British Empire follow suit.
1914 World War I: Battle of Cer begins.
1914 World War I: attle of Stalluponen
1914 World War I: German forces occupy Brussels.
1914 World War I: in Belgium, British and German troops clash for the first time in the war.
1914 World War I: Japan declares war on Germany and bombs Qingdao, China.
1914 World War I: German troops capture Namur.
1914 World War I: the Royal Navy defeats the German fleet in the Battle of Heligoland Bight.
1914 World War I: Private Thomas Highgate becomes the first British soldier to be executed for desertion during the war.
1914 World War I: The creation of the Canadian Automobile Machine Gun Brigade, the first fully mechanized unit in the British Army.
1914 World War I: South African troops open hostilities in German south-west Africa (Namibia) with an assault on the Ramansdrift police station.
1914 World War I: The Battle of Aisne begins between Germany and France.
1914 The Irish Home Rule Act becomes law, but is delayed until after World War I.
1914 World War I: South African troops land in German South West Africa.
1914 World War I: first aerial combat resulting in a kill.
1914 World War I: iege of Antwerp
1914 World War I: The British super-dreadnought battleship HMS Audacious (23,400 tons), is sunk off Tory Island, north-west of Ireland, by a minefield laid by the armed German merchant-cruiser ''Berlin''.
1914 World War I: the first British Royal Navy defeat of the war with Germany, the Battle of Coronel, is fought off of the western coast of Chile, in the Pacific, with the loss of HMS Good Hope and HMS Monmouth.
1914 World War I: Following a war-induced closure in July, the New York Stock Exchange re-opens for bond trading.
1914 World War I: The Serbian Army recaptures Belgrade from the invading Austro-Hungarian Army.
1914 World War I: German battleships under Franz von Hipper bombard the English ports of Hartlepool and Scarborough.
1914 World War I: Australian and New Zealand troops arrive in Cairo, Egypt.
1914 World War I: The "Christmas truce" begins.
1914 World War I: Known as the Christmas truce, German and British troops on the Western Front temporarily cease fire.
1915 World War I: German zeppelins bomb the towns of Great Yarmouth and King's Lynn in the United Kingdom killing more than 20, in the first major aerial bombardment of a civilian target.
1915 World War I: Germany uses poison gas against Russia
1915 World War I: Germany institutes unrestricted submarine warfare.
1915 World War I: Cornered off the coast of Chile by the Royal Navy after fleeing the Battle of the Falkland Islands, the German light cruiser SMS ''Dresden'' is abandoned and scuttled by her crew.
1915 World War I: Massive naval attack in Battle of Gallipoli. Three battleships are sunk during a failed British and French naval attack on the Dardanelles.
1915 French pilot Roland Garros is shot down and glides to a landing on the German side of the lines during World War I.
1915 World War I: The Battle of Gallipoli begins—The invasion of the Turkish Gallipoli Peninsula by Australian, British, French and New Zealand troops begins with landings at Anzac Cove and Cape Helles.
1915 World War I: German submarine {{SMU|U-20}} sinks {{RMS|Lusitania}}, killing 1,198 people including 128 Americans. Public reaction to the sinking turns many formerly pro-Germans in the United States against the German Empire.
1915 World War I: Second Battle of Artois between German and French forces.
1915 World War I: Italy joins the Allies after they declare war on Austria-Hungary.
1915 World War I: Italy declares war on Austria-Hungary.
1915 World War I: end of First Battle of the Isonzo.
1915 World War I: The Second Battle of Champagne begins.
1915 Bulgaria enters World War I as one of the Central Powers.
1915 World War I: British nurse Edith Cavell is executed by a German firing squad for helping Allied soldiers escape from Belgium
1915 World War I: Last Australian troops evacuated from Gallipoli.
1916 World War I: The Battle of Gallipoli concludes with an Ottoman Empire victory when the last Allied forces are evacuated from the peninsula.
1916 World War I: Paris is first bombed by German zeppelins.
1916 World War I: In France, the Battle of Verdun begins.
1916 World War I: The attle of Verdun
1916 World War I: The British 6th Indian Division surrenders to Ottoman Forces at the Siege of Kut in one of the largest surrenders of British forces up to that point.
1916 World War I: attle of Jutland
1916 World War I: the Battle of the Somme begins with a week-long artillery bombardment on the German Line.
1916 World War I: irst day on the Somme
1916 World War I: attle of Fromelles
1916 World War I: In Armenia, Russian troops capture Gumiskhanek.
1916 World War I: Austrian sabotage causes the sinking of the Italian battleship ''Leonardo da Vinci'' in Taranto.
1916 Romania declares war against Austria-Hungary, entering World War I as one of the Allied nations.
1916 World War I: Tanks are used for the first time in battle, at the Battle of the Somme.
1916 World War I: Manfred von Richthofen ("The Red Baron"), a flying ace of the German Luftstreitkräfte, wins his first aerial combat near Cambrai, France.
1916 World War I: First Battle of the Somme ends – In France, British Expeditionary Force commander Douglas Haig calls off the battle which started on July 1, 1916.
1916 World War I: A mine explodes and sinks HMHS Britannic in the Aegean Sea, killing 30 people.
1916 World War I: The Central Powers capture Bucharest.
1916 World War I: The Battle of Verdun ends when German forces under Chief of Staff Erich Von Falkenhayn are defeated by the French and British, and suffer 337,000 casualties.
1916 World War I: attle of Verdun
1917 World War I: President Woodrow Wilson of the still-neutral United States calls for "peace without victory" in Europe.
1917 World War I: The United States breaks off diplomatic relations with Germany a day after the latter announced a new policy of unrestricted submarine warfare.
1917 World War I: The U.S. ambassador to the United Kingdom is given the Zimmermann Telegram, in which Germany pledges to ensure the return of New Mexico, Texas, and Arizona to Mexico if Mexico declares war on the United States.
1917 World War I: Baghdad falls to Anglo-Indian forces commanded by General Stanley Maude.
1917 World War I: irst Battle of Gaza
1917 World War I: President Woodrow Wilson asks the U.S. Congress for a declaration of war on Germany.
1917 World War I: The United States declares war on Germany (see President Woodrow Wilson's address to Congress).
1917 World War I: Canadian forces successfully complete the taking of Vimy Ridge from the Germans.
1917 World War I: The Selective Service Act of 1917 is passed, giving the President of the United States the power of conscription.
1917 World War I: Conscription begins in the United States as "Army registration day".
1917 World War I: attle of Messines
1917 World War I: the deadliest German air raid on London during World War I is carried out by Gotha G bombers and results in 162 deaths, including 46 children, and 432 injuries.
1917 World War I: the deadliest German air raid on London during World War I is carried out by Gotha G bombers and results in 162 deaths, including 46 children, and 432 injuries.
1917 The first U.S. troops arrive in France to fight alongside Britain, France, Italy, and Russia against Germany, and Austria-Hungary in World War I.
1917 World War I: Arabian troops led by T. E. Lawrence ("Lawrence of Arabia") and Auda ibu Tayi capture Aqaba from the Ottoman Empire during the Arab Revolt.
1917 World War I: The Corfu Declaration, which leads to the creation of the post-war Kingdom of Yugoslavia, is signed by the Yugoslav Committee and Kingdom of Serbia.
1917 World War I: The First Battle of Passchendaele takes place resulting in the largest single day loss of life in New Zealand history.
1917 World War I: At Vincennes outside of Paris, Dutch dancer Mata Hari is executed by firing squad for spying for the German Empire.
1917 First British bombing of Germany in World War I.
1917 Battle of Caporetto; Italy suffers a catastrophic defeat at the forces of Austria-Hungary and Germany on the Austro-Italian front of World War I (lasts until 19 November - also called Twelfth Battle of the Isonzo).
1917 World War I: Battle of Caporetto; Italy suffers a catastrophic defeat at the forces of Austria-Hungary and Germany. The young unknown Oberleutnant Erwin Rommel captures Mount Matajur with only 100 Germans against a force of over 7000 Italians.
1917 World War I: attle of Beersheba (1917)|Battle of Beersheba
1917 World War I: Third Battle of Ypres ends: After three months of fierce fighting, Canadian forces take Passchendaele in Belgium.
1917 World War I: Third Battle of Gaza ends: British forces capture Gaza from the Ottoman Empire.
1917 World War I: Battle of Cambrai begins – British forces make early progress in an attack on German positions but are later pushed back.
1917 World War I: The United States declares war on Austria-Hungary.
1918 Germany, Austria and Russia sign the Treaty of Brest-Litovsk ending Russia's involvement in World War I, and leading to the independence of Finland, Estonia, Latvia, Lithuania and Poland.
1918 World War I: The first phase of the German Spring Offensive, Operation Michael, begins.
1918 World War I: Second Battle of the Somme ends.
1918 World War I: Actors Douglas Fairbanks and Charlie Chaplin sell war bonds on the streets of New York City's financial district.
1918 World War I: German fighter ace Manfred von Richthofen, known as "The Red Baron", is shot down and killed over Vaux-sur-Somme in France.
1918 World War I, Western Front: attle for Belleau Wood
1918 World War I: attle of Belleau Wood
1918 World War I, Western Front: attle for Belleau Wood
1918 World War I: the Second Battle of the Marne begins near the River Marne with a German attack.
1918 Japan announces that it is deploying troops to Siberia in the aftermath of World War I.
1918 World War I: the Battle of Amiens begins a string of almost continuous victories with a push through the German front lines (Hundred Days Offensive).
1918 World War I: the Battle of Amiens ends.
1918 World War I: The Second Battle of the Somme begins.
1918 World War I: The Meuse-Argonne Offensive, the bloodiest single battle in American history, begins.
1918 World War I: The Hindenburg Line is broken by Allied forces. Bulgaria signs an armistice.
1918 World War I: Arab forces under T. E. Lawrence (a/k/a "Lawrence of Arabia") capture Damascus.
1918 World War I: In the Argonne Forest in France, United States Corporal Alvin C. York leads an attack that kills 25 German soldiers and captures 132.
1918 Mehmed Talat Pasha and the Young Turk (C.U.P.) ministry resign and sign an armistice, ending Ottoman participation in World War I.
1918 World War I: Czechoslovakia is granted independence from Austria-Hungary marking the beginning of independent Czechoslovak state, after 300 years.
1918 The Ottoman Empire signs an armistice with the Allies, ending the First World War in the Middle East.
1918 World War I: Austria-Hungary surrenders to Italy.
1918 World War I: Germany signs an armistice agreement with the Allies in a railroad car outside Compiègne in France. The war officially ends at 11:00 (The eleventh hour of the eleventh day of the eleventh month) and this is annually honoured with a two-minute silence.
1918 U.S. President Woodrow Wilson sails for the World War I peace talks in Versailles, becoming the first US president to travel to Europe while in office.
1919 World War I: The Paris Peace Conference opens in Versailles, France.
1919 Eugene V. Debs enters prison at the Atlanta Federal Penitentiary in Atlanta, Georgia, for speaking out against the draft during World War I.
1919 Edward George Honey first proposes the idea of a moment of silence to commemorate The Armistice of World War I, which later results in the creation of Remembrance Day. In the United States it was called Armistice Day and is now Veterans Day.
1919 Admiral Ludwig von Reuter scuttles the German fleet in Scapa Flow, Orkney. The nine sailors killed are the last casualties of World War I.
1919 The Treaty of Versailles is signed in Paris, formally ending World War I between Belgium, Britain, France, Italy, the United States and allies on the one side and Germany and Austria-Hungary on the other side.
1919 Following Peace Day celebrations marking the end of World War I, ex-servicemen riot and burn down Luton Town Hall.
1920 The League of Nations holds its first meeting, and ratifies the Treaty of Versailles, therefore ending World War I.
1920 World War I: Ottoman sultan Mehmed VI's representatives sign the Treaty of Sèvres that divides up the Ottoman Empire between the Allies.
1921 A symbolic Tomb of the Unknown Soldier is installed beneath the Arc de Triomphe in Paris to honor the unknown dead of World War I.
1923 Occupation of the Ruhr: Troops from France and Belgium occupy the Ruhr area to force Germany to make its World War I reparation payments.
1923 The Treaty of Lausanne, settling the boundaries of modern Turkey, is signed in Switzerland by Greece, Bulgaria and other countries that fought in World War I.
1923 The great powers of World War I withdraw from Istanbul
1925 World War I aftermath: The final Locarno Treaty is signed in London, establishing post-war territorial settlements.
1932 World War I Veterans begin to assemble in Washington, DC in the Bonus Army to request cash bonuses promised to them to be paid in 1945.
1932 Bonus Army: around a thousand World War I veterans amass at the United States Capitol as the U.S. Senate considers a bill that would give them certain benefits.
1932 In Washington, D.C., police fire tear gas on World War I veterans part of the Bonus Expeditionary Force who attempt to march to the White House.
1932 Great Depression: in Washington, D.C., troops disperse the last of the "Bonus Army" of World War I veterans.
1943 A Luftwaffe bombing raid on the harbour of Bari, Italy, sinks numerous cargo and transport ships, including an American Liberty ship, the John Harvey, with a stockpile of World War I-era mustard gas.
1994 Eugene Bullard, The only black pilot in World War I, is posthumously commissioned as Second Lieutenant in the United States Air Force.