Jun 1914: Franz Ferdinand, heir to the throne of the Austro-Hungarian Empire, and his wife are assassinated in Sarajevo by Serb nationalist Gavrilo Princip
Jul 1914: Austria-Hungary declares war on Serbia, Russia pledges to protect Serbia
Aug 1914: Germany, ally of Austria, declares war on Russia, on Russia's ally France and on neutral Belgium in order to attack France ("Schlieffen Plan"); France's ally Britain declares war on Germany, Austria-Hungary declares war on Russia; Germany attacks Russia and its general Erich Ludendorff wins the Battle of Tannenberg; Britain and France declare war on Austria-Hungary; Japan declares war on Germany and Austria; the German army defeats the French army at the Battle of the Ardennes
Sep 1914: As German troops advance from the north, France transfers its government from Paris to Bordeaux for two months; German warplanes bomb Paris; British warplanes bomb Duesseldorf and Koeln/Cologne; the French army and the British Expeditionary Force stop the German advance in France ("Battle of the Marne") just before they reach Paris; Australia captures German New Guinea; Russia defeats Austria in Galicia (a Polish-Ukrainian region of Austria) and attacks Hungary; Germany fails to invade Poland (a region of Russia); Germany appoints Paul von Hindenburg commander of the eastern (Russian) front;
Oct 1914: Ottoman warships bomb Odessa and Sevastopol in Russia; Britain promises independence to the Sherif of Mecca in return for military alliance against the Ottoman Empire;
Nov 1914: Russia declares war on Ottoman Empire; Britain and France declare war on the Ottoman Empire; Ottoman Empire attacks Serbia; Britain annexes Ottoman Cyprus, occupies Ottoman southern Iraq and a British submarine enters the Ottoman-controlled Dardanelles; Japan conquers German Tsingtau in China; Russia bombs Ottoman Trebizond; The British navy begins a naval blockade of Germany; Russian troops led by Georgy Bergmann attack the Ottoman Caucasus;
Dec 1914: Austria conquers Serbia; the British navy defeats the German navy at the Falkland Islands; Russia withdraws from Hungary; the Ottomans attack Russian Caucasus but are defeated at the Battle of Sarikamish; Britain proclaims a protectorate over Egypt, conquered by Australian and New Zealand troops, with Hussein Kamel Pasha as the new sultan; German warplanes bomb England; French and German soldiers in the trenches observe an unofficial Christmas truce
Jan 1915: German zeppelins bomb England
Feb 1915: Germany begins a submarine (U-boat) blockade of Britain (first unrestricted submarine warfare against merchant vessels);
Mar 1915: The Austrian fort of Przemysl in Galicia surrenders to the Russians after a 133-day siege; German submarines sink the British passenger ship "Falaba";
Apr 1915: British troops land at Gallipoli; the Ottomans begin deportations and massacres of Armenians that will kill more than a million civilians; Germany uses poison gas on the French front during the second Battle of Ypres;
May 1915: British and French troops land at the Dardanelles while the Russian navy bombs Bosphorus forts; German submarines (U-boats) sinks the British passenger ship "Lusitania" killing 1,198 civilians, including 128 citizens of the USA; Russia invades Ottoman Armenia; Italy declares war against Austria; China cedes territories to Japan in order to avoid war; South African troops conquer German South-West Africa (Namibia);
Jul 1915: Bulgaria joins the alliance of Austria-Hungary, Germany and Ottoman Empire; Austria and Germany invade Russian Poland;
Aug 1915: Germany enters Warsaw and the Ottomans reconquer Armenia; Britain and Russian occupy Iran to establish a corridor; Italy declares war on the Ottoman Empire;
Sep 1915: British poison gas at the Battle of Loos accidentally kills thousands of British soldiers; Germany suspends its unrestricted submarine warfare; German corporal Hauptmann Rohr introduces a new war tactic based on the "sturmtruppen" (storm troops);
Oct 1915: The Fokker plane gives Germany supremacy in the air; Bulgaria declares war on Serbia, while France, Britain, Russia and Italy declare war on Bulgaria; French and British forces land at Salonika and advance into Macedonia against Austria and Bulgaria (soldiers will die more of malaria than of battle); Austria enters Serbia's capital Belgrade;
Nov 1915: The Pact of London is signed by Britain, France, Russia, Japan, and Italy;
Dec 1915: The Ottoman Empire defeats Britain at Gallipoli; Austria, the Ottomans and Bulgaria conquer Serbia; Mark Sykes of Britain and Francois Picot of France agree to split the Ottoman Empire in spheres of influence;
Mar 1916: Germany declares war on Portugal; Germany resumes unrestricted submarine warfare but only for two months;
Apr 1916: British troops surrender to the Ottomans at Kut in Iraq;
Jun 1916: The British and German navies fight the Battle of Jutland with no winner (but the British lose more ships and more sailors);
Jul 1916: Britain launches an offensive against Germany at the Battle of the Somme using tanks for the first time in history;
Aug 1916: Italy declares war on Germany: Romania declares war to Austria, Germany and the Ottomans; After protests against Greek king Konstantinos I's policy of neutrality that allows Bulgary to occupy parts of Macedonia, army officers install a provisional government in Thessaloniki led by prime minister Eleftherios Venizelos that declares war on Austria, Germany and the Ottomans; Germany appoints Erich Ludendorff as joint leader (with Paul von Hindenburg) of the war effort;
Sep 1916: Germany builds the "Hindenburg line", a defensive line;
Oct 1916: Austria's prime minister Karl Stuergkh is assassinated by a socialist;
Nov 1916: The Battle of the Somme ends with no winner but one million casualties; Franz Josef of Austria dies and is succeeded by his great-nephew Karl;
Dec 1916: Germany occupies Romania; Britain and France conquer Togoland, a German colony in Africa;
Dec 1916: The Battle of Verdun ends after ten months with no winner (the longest battle of the war, with one million casualties);
1917: Loss of labor, fertilizer and horses and declining railroads cause hunger throughout Europe that causes popular riots;
Jan 1917: Britain's Room 40 intercepts a secret telegram sent by Germany to Mexico (the "Zimmermann telegram");
Jan 1917: 150,000 workers march in Russia's capital St Petersburg to protest against hunger and war;
Feb 1917: Germany begins a third unrestricted submarine warfare campaign; Britain recapture Kut; Talat is appointed grand vizier of the Ottoman Empire;
Mar 1917: Britain captures Baghdad; Female textile workers take to the streets in Russia to protest against hunger and war, beginning a protest that turns into a general strike and an army mutiny and causes the Russian czar Nicholas II to abdicate;
Apr 1917: The USA declares war on Germany; France loses tens of thousands of soldiers trying to push back the Germans at Chemin des Dames; Britain captures most of Iraq; French troops mutiny; Lenin arrives in St Petersburg;
May 1917: Philippe Petain is appointed commander-in-chief of the French Army; Mihaly Karolyi organizes anti-Austrian demonstrations in Hungary with help from the socialists;
Jun 1917: Following a British blockade of Greece and a French landing at the port of Athens, Greek king Konstantinos I flees Greece surrendering power to his prime minister Eleftherios Venizelos;
Jul 1917: Arab militias led by Lawrence of Arabia seize the Jordanian port of Aqaba; The USA lands in France;
Aug 1917: Anti-war demonstrations in Italy, led by women, leave 41 people dead; China declares war on Austria, Germany and the Ottoman Empire
Nov 1917: The third Battle of Ypres ends after months of fighting with no winner but 700,000 casualties; Britain wins the battle of Cambrai thanks to its 378 tanks; Lenin's Bolshevik party seizes power in Russia; Austria and Germany defeat Italy at the Battle of Caporetto; The British government promises a Jewish state in Palestine ("Balfour Declaration");
Dec 1917: Russia signs an armistice with Germany, having lost Poland, Lithuania, Estonia, Livonia and Coutland, and allowing Germany to shift many divisions to the French front; Britain captures Jerusalem from the Ottomans with help from Sherif Hussein's son Feisal;
1918: Hundreds of thousands of people have died of famine in Syria since 1915; The USA, Britain and France produce an average of 11,000 warplanes per month;
Jan 1918: Massive workers' strikes take place in Austria and Germany; US president Woodrow Wilson delivers the "14 points" speech for a future of peace, including dismantling the Austrian and Ottoman empires and independence for Poland from Russia;
Feb 1918: Germany captures Estonia; Austria, Germany and the Ottomans sign a protectorate treaty with Ukraine;
Mar 1918: Russia signs a peace treaty with Germany and Austria (Treaty of Brest-Litovsk), returning occupied cities to the Ottomans, acknowledging the independence of Transcaucasia (Armenia, Georgia, Azerbaijan), ceding the Baltic states (Lithuania, Latvia, Estonia) to Germany, recognizing the independence of Ukraine, and allowing German occupation of western Russia from Poland down to almost the Caspian Sea (at the cost of one million German soldiers deployed into Russia); Germany launches a spring offensive in France and Germany breaks through on the Somme; German troops begin an artillery bombardment of Paris; Germany captures Kiev;
Apr 1918: Germany launches an offensive in the Flanders; Germany occupies eastern Ukraine for its coal; The USA has 2 million soldiers in Europe, Britain has 1.8 million in France, France has 1.7 million;
May 1918: The Ottomans invade Armenia; Romania surrenders, losing Wallachia to Austria and southern regions to Bulgaria;
Jun 1918: The USA defeats the Germans at the Battle of Belleau Wood, marking the nearest that German troops ever got to Paris
Jun 1918: The German empire has reached its greatest extent, from almost Paris to Ukraine, from the Baltic states to Caucasus
1918: An influenza pandemic kills 20 million people worldwide
Aug 1918: France, Britain and the USA launch a counter-offensives on the Somme and push German troops back to the "Hindenburg line"; 1,800 British and French airplanes and over 400 tanks are used in the Battle of Amiens, causing massive disertions in the German army;
Sep 1918: Britain defeats the Ottomans in the Middle East (Battle of Megiddo); 300,000 US troops attack German troops at the Battle of St Mihiel in France; French, British, Serbian and Greek troops defeat the Bulgarian troops at Dobro Polje and Bulgaria surrenders, breaking the land links between Germany and the Ottomans and between Austria and Ukraine; Britain, France and the USA breach the "Hindenburg line";
Oct 1918: Britain captures Damascus; the German navy mutinies; German chancellor Georg von Hertling is replaced by Max von Baden; the Ottomans surrender opening the Dardanelle and Bosporus straits to British warships and evacuating the Arab provinces (Treaty of Mudros); US president Wilson pledges support for the independence of Czechoslovakia and Yugoslavia and refuses to negotiate with Austria; Ludendorff resigns;
Nov 1918: Britain captures Mosal in Iraq (after the war has already ended); Following a general strike in Berlin, German kaiser Wilhelm II abdicates and Germany becomes a republic; Italy defeats the Austro-Hungarian army at the Battle of Vittorio Veneto and conquers Trento and Trieste; Germany and Austria surrender and the war ends; Austria proclaims the republic; German troops surrender in East Africa and Zambia; Serbian troops reenter their capital Belgrade; King Albert I reenters Belgium's capital Bruxelles; France reenters Alsace and Lorraine after more than 40 years of German occupation;
Dec 1918: The kingdom of Serbia, Croatia and Slovenia (Yugoslavia) is created
Jan 1919: A peace conference is convened in Paris
Jun 1919: A peace treaty is signed in Versailles according to which Germany loses 13% of its territory and 10% of its population and is forced to pay reparations (mainly to France);
Dec 1919: John Maynard Keynes's "The Economic Consequences of the Peace", that argues the peace treaty was unfair to Germany, becomes a world bestseller;
Jan 1920: The League of Nations meets in London
Apr 1920: The Ottoman Empire is dismantled at the Conference of Sanremo