June 28, 1914:       Assassination of Archduke Franz Ferdinand, heir to the throne of Austro-Hungarian empire, in Sarajevo, Bosnia
July 28, 1914:       Begining of the World War - I, when Austria-Hungary declared war on Serbia.
July 29 - December 09, 1914:       Austria-Hungary repeatedly invades Serbia but is repeatedly repulsed
August 01, 1914:       Outbreak of war - Germany declares war on Russia
August 03, 1914:       Germany declares war on France
August 04, 1914:       Germany invades neutral Belgium; Britain declares war on Germany; US President Woodrow Wilson declares policy of US neutrality.
August 14, 1914:        Battle of the Frontiers begins
August 17-19, 1914:       Russia invades East Prussia
August 23, 1914:       Japan declares war on Germany
August 23, 1914 - September 2, 1914:       Austria-Hungary invades Russian Poland (Galicia)
August 26-30, 1914:       Battle of Tannenberg, which Russia loses; Germany's greatest success of the war on Eastern Front
September 5-10, 1914:       First Battle of Marne, halts German advance, resulting in stalemate and trench warfare
September 9-14, 1914:       First Battle of Masurian Lakes, which Russia loses
September 14, 1914:       First Battle of Aisne begins
September 15- November 24, 1914:       The "race to the sea", trenches appear on September 15
September 17-28, 1914:       Austro-German attack on western Poland
October 14 - November 22, 1914:       First Battle of Ypres
October 29, 1914:       Turkey enters the war on the side of the Central Powers
December 08, 1914:       Battle of the Falkland Islands
December 21, 1914:       First German air raid on Britain
December 25, 1914:       Unofficial Christmas truce declared by soldiers along the Western Front
January 01, 1915 - March 30, 1915:       Allied offensive in Artois and Champagne
January 15, 1915:       Japan's 21 demands on China
January 19-20, 1915:       First German zeppelin attack on England
February 04, 1915:       German U-boat attacks on Allied and neutral shipping; declares blockade of Britain
February 7-21, 1915:       Russians suffer heavy losses at Second Battle of Masurian Lakes (also known as the Winter Battle)
February 19, 1915:       Allied amphibious attack on the Dardanelles and Gallipoli (initiated by Winston Churchill, who resigns as a consequence) ends with the Turkish siege of the Allied forces in August, 1915.
March 01, 1915:       First passenger ship sinks, the British liner Falaba
March 11, 1915:       Britain announces blockade of German ports
April-June, 1915:       Germans focus on Eastern Front, breaking through Gorlice-Tarnow and forcing Russia out of much of Poland
April 22 - May 25, 1915:       First use of poison gas by Germany starts Second Battle of Ypres
April 25, 1915:       Allied landing at Gallipoli
April 26, 1915:       France, Russia, Italy and Britain conclude secret Treaty of London
May 02, 1915:       Austro-German offensive on Galicia begins
May 07, 1915:       U-boat sinks British liner Lusitania with the loss of American lives, creating a US-German diplomatic crisis
May 09, 1915:       Second Battle of Artois begins
May 23, 1915:       Ignoring treaty agreements with the Central Powers, Italy declares war on Austria-Hungary
June 29 - December 2, 1915:       Italians launch unsuccessful attack on Hungarians at 1st, 2nd, 3rd & 4th Battles of Isonzo; there are to be 12 in total
August 04, 1915:       Germans capture Warsaw
September 05, 1915:       Tsar Nicholas takes command of Russian armies
September 22, 1915:       Second Battle of Champagne begins
October 03, 1915:       Anglo-French force lands at Salonika in Greece
October - November, 1915:       Austro-German-Bulgarian forces invade Serbia, expelling Serbian army from the country
December 19, 1915:    Sir Douglas Haig replaces Sir John French as commander of British Expeditionary Force
December 28, 1915:    Allies begin withdrawal of troops from Gallipoli
February 21 - December 18, 1916:    German attack on Verdun in the longest battle of the war, ultimately defended by the French at great cost to both sides
March 11 - November 14, 1916:    5th, 6th, 7th, 8th and 9th Battles of Isonzo between Italy and Austria-Hungary
April, 1916:    British forces in Mesopotamia begin advance on Baghdad
March 09, 1916:    Pancho Villa's raid on Columbus, New Mexico
March 24, 1916:    French passenger ship, Sussex, torpedoed
April 24, 1916:    Easter rebellion starts in Ireland
May 04, 1916:    Germany renounces submarine policy
May 19, 1916:    Britain and France conclude Sykes-Picot agreement
May 31 - June 01, 1916:    Battle of Jutland, the biggest naval battle in history, ultimately without a clear victor
June - August, 1916:    Turkish forces, led by Enver Pasha, are defeated by the Russians in the Caucasus
June 04 - September 20, 1916:    Russian Brusilov offensive in Carpathia nearly knocks Austria-Hungary out of the war
June 05, 1916:    With British support (led by T.E. Lawrence), Hussein, grand sherif of Mecca, lead an Arab revolt against the Turks in the Hejaz
July 01, 1916:    Start of the Battle of the Somme, with the greatest number of casualties in British military history, 60,000
July 29, 1916:    US marines land in Haiti
August - December, 1916:    Romania enters the war with the Allies, but is quickly overrun by German forces
August 28, 1916:    Italy declares war on Germany
August 31, 1916:    Germany suspends submarine assaults
September 15, 1916:    Tanks introduced for the first time on the Somme battlefield by the British
October 15, 1916:    Germany resumes U-boat attacks
November 07-09, 1916:    US President Woodrow Wilson secures re-election
November 18, 1916:    End of the Battle of the Somme
November 28, 1916:    First German airplane (as opposed to zeppelin) air-raid on Britain
November 29, 1916:    US occupation of Santa Domingo proclaimed
December 07, 1916:    David Lloyd George replaces Asquith as British Prime Minister
December 12, 1916:    Germany issues peace note suggesting compromise peace
December 18, 1916:    US President Woodrow Wilson requests statements of war objectives from warring nations in peace note
January 10, 1917:    Allies state peace objectives in response to US President Woodrow Wilson's December 1916 peace note
January 31, 1917:    Germany announces unrestricted submarine warfare
February 01, 1917:    Germany resumes unrestricted submarine warfare
February 03, 1917:    US severs diplomatic ties with Germany
February 23 - April 05, 1917:    German forces begin withdrawal to strong positions on the Hindenburg Line
February 24, 1917:    Zimmermann Telegram is passed to the US by Britain, detailing alleged German proposal of an alliance with Mexico against the US
February 26, 1917:    US President Woodrow Wilson requests permission from Congress to arm US merchantmen
March 01, 1917:    Zimmermann Telegram published in US press
March 11, 1917:    British capture Baghdad
March 12, 1917:    US President Woodrow Wilson announces arming of US merchantmen by executive order after failing to win approval from Congress
March 15, 1917:    Tsar Nicholas II abdicates as a consequence of Russian Revolution
March 20, 1917:    US President Woodrow Wilson's war cabinet votes unanimously in favour of declaring war on Germany
April 02, 1917:    US President Woodrow Wilson delivers war address to Congress
April 06, 1917:    US declares war on Germany
April 09-20, 1917:    Nivelle Offensive (Second Battle of Aisne, Third Battle of Champagne) ends in French failure
April 09, 1917:    Canadian success at the Battle of Vimy Ridge
April 16, 1917:    Lenin arrives in Russia
April 29 - May 20, 1917:    Mutiny breaks out among French army
May 12 - October 24, 1917:    10th, 11th and 12th Battles of Isonzo fought, ending in Italian failure
May 28, 1917:    Pershing leaves New York for France
June 07, 1917:    British explode 19 large mines under the Messines Ridge
June 15, 1917:    US Espionage Act passed
June 26, 1917:    First US troops arrive in France, 1st Division
June 27, 1917:    Greece enters the war on the side of the Allies
July 02, 1917:    Pershing makes first request for army of 1,000,000 men
July 06, 1917:    T.E. Lawrence and the Arabs capture Aquaba
July 11, 1917:    Pershing revises army request figures upwards to 3,000,000
July 16, 1917:    Third Battles of Ypres (Passchendaele) begins
July 31, 1917:    Major British offensive launched at Ypres.
September 01, 1917:    Germany takes the northernmost end of the Russian front in the Riga offensive
October 24, 1917:    Austria-Germany breakthrough at Caporetto on Italian front
November 07, 1917:    Bolshevik Revolution in Russia results in Communist government under Lenin taking office
November 20, 1917:    British launch surprise tank attack at Cambrai
December 07, 1917:    US declares war on Austria-Hungary
December 09, 1917:    Jerusalem falls to Britain
December 22, 1917:    Russia opens separate peace negotiations with Germany (Brest-Litovsk)
January - September, 1918:    T.E. Lawrence leads Arab guerrillas in successful campaign against Turkish positions in Arabia and Palestine
January 08, 1918:    US President Woodrow Wilson makes "Fourteen Points" speech to Congress
February 11, 1918:    US President Woodrow Wilson makes "Four Principles" speech to Congress
March 03, 1918:    Soviet Russia concludes separate peace negotiations in treaty of Brest-Litovsk
March 21, 1918:    Germany launches Spring push, eventually mounting five major offensives against Allied forces, starting with the Battle of Picardy against the British
March 26, 1918:    Doullens Agreement gives General Ferdinand Foch "co-ordinating authority" over the Western Front
April 09, 1918:    Germany launches second Spring offensive, the Battle of the Lys, in the British sector of Armentieres
April 14, 1918:    Foch appointed Commander-in-Chief of Allied forces on Western Front
May 25, 1918:    German U-boats appear in US waters for first time
May 27, 1918:    Third German Spring offensive, Third Battle of the Aisne, begins in French sector along Chemin des Dames
May 28, 1918:    US forces (28th Regiment of 1st Division) victorious in first major action, Battle of Cantigny
June 06, 1918:    US 3rd Division captures Bouresches and southern part of Belleau Wood
June 09, 1918:    Germans launch fourth Spring offensive, Battle of the Matz, in French sector between Noyan and Montdider
June 15, 1918:    Italians prevail against Austro-Hungarian forces at Battle of Piave
July 06, 1918:    US President Woodrow Wilson agrees to US intervention in Siberia
July 15, 1918:    Final phase of great German Spring push, the Second Battle of Marne, begins
July 16-17, 1918:    Former Tsar Nicholas II, his wife, and children, are murdered by the Bolsheviks
July 18, 1918:    Allies counterattack against German forces, seizing initiative
August 03, 1918:    Allied intervention begins at Vladivosto
August 08, 1918:    Haig directs start of successful Amiens offensive, forcing all German troops back to the Hindenburg Line; Ludendorff calls it a "black day" for German army
September 12, 1918:    US forces clear the St.-Mihiel salient, during which the greatest air assault of the war is launched by the US
September 19, 1918:    Start of British offensive in Palestine, the Battle of Megiddo
September 26, 1918:    Battle of the Vardar pits Serb, Czech, Italian, French and British forces against Bulgarian forces
September 26, 1918:    Meuse-Argonne offensive opens; the final Franco-American offensive of the war
September 27 - October 17, 1918:    Haig's forces storm the Hindenburg Line, breaking through at several points
September 29, 1918:    Bulgaria concludes armistice negotiations
September 28 - October 14, 1918:    Belgian troops attack at Ypres
October 03-04, 1918:    Germany and Austria send peace notes to US President Woodrow Wilson requesting an armistice
October 17 - November 11, 1918:    British advance to the Sambre and Schledt rivers, taking many German prisoners
October 21, 1918:    Germany ceases unrestricted submarine warfare
October 27, 1918:    Erich Ludendorff resigns
October 30, 1918:    Turkey concludes an armistice with the Allies
November 03, 1918:    German fleet mutinies at Kiel; Trieste falls to the Allies; Austria-Hungary concludes an armistice
November 7-11, 1918:    Germany negotiates an armistice with the Allies in Ferdinand Foch's railway carriage headquarters at Compiegne
November 09, 1918:    Kaiser Wilhelm II abdicates
November 10, 1918:    Kaiser Wilhelm II flees to Holland; German republic is founded
November 11, 1918:    Armistice day; fighting ceases at 11am
January 10-15, 1919:    Communist revolt in Berlin
January 18, 1919:    Start of peace negotiations in Paris
January 25, 1919:    Peace conference accepts principle of a League of Nations
February 06, 1919:    German National Assembly meets in Weimar
February 14, 1919:    Draft covenant of League of Nations completed
May 06, 1919:    Peace conference disposes of German colonies
May 07- June 28, 1919:    Treaty of Versailles drafted and signed

Source:     http:   //firstworldwar.com/