From first shot to silence of peace: Timeline of World War I

From first shot to silence of peace: Timeline of World War I
ONE OF ONE HUNDRED PHOTOS WORLD WAR ONE CENTENARY TIMELINE-In this June 28, 1914 file photo, the Archduke of Austria Franz Ferdinand, center right, and his wife Sophie, center left, walk to their a car in Sarajevo. This photo was taken minutes before the assassination of the Archduke and his wife, an event which set off a chain reaction of events which would eventually lead to World War One. (AP Photo, File)

PARIS (AP) — Unleashed by an archduke's assassination, World War I gradually entangled more and more countries, killing millions of soldiers and civilians and touching multiple continents.

As the world marks 100 years since the fighting stopped, here is a look at some key moments in WWI:

1914

June 28: Serb teenager Gavrilo Princip kills Austrian Archduke Franz Ferdinand

July 28: Austria-Hungary declares war on Serbia

THIRTY EIGHT OF ONE HUNDRED PHOTOS WORLD WAR ONE CENTENARY TIMELINE-In this 1915 file photo, Turkish soldiers form a queue to get water from a fountain, behind their lines in Gallipoli, Turkey. (AP Photo, File)
THIRTY EIGHT OF ONE HUNDRED PHOTOS WORLD WAR ONE CENTENARY TIMELINE-In this 1915 file photo, Turkish soldiers form a queue to get water from a fountain, behind their lines in Gallipoli, Turkey. (AP Photo, File) (AP)

Aug. 1: Germany declares war on Russia

Aug. 3: Germany declares war on France

Aug. 4: Germany invades Belgium; Britain declares war on Germany

Aug. 23: Japan declares war on Germany

September: Battle of the Marne stops the German advance in France

Oct. 29: Ottoman Empire enters the war

November: Beginning of trench warfare

Dec. 25: Unofficial Christmas Truce

1915

February: German U-boat campaign marks first large use of submarines in warfare

SEVENTY OF ONE HUNDRED PHOTOS WORLD WAR ONE CENTENARY TIMELINE-In this undated file photo, dancer "Mata Hari", who was born Margaretha Geertruida Zelle poses in an unknown location. Zelle was executed October 15, 1917 during World War One for spying for Germany. (AP Photo, File)
SEVENTY OF ONE HUNDRED PHOTOS WORLD WAR ONE CENTENARY TIMELINE-In this undated file photo, dancer "Mata Hari", who was born Margaretha Geertruida Zelle poses in an unknown location. Zelle was executed October 15, 1917 during World War One for spying for Germany. (AP Photo, File) (ASSOCIATED PRESS)

April: Allied troops land in Gallipoli , Turkey, a defining moment for Australian, New Zealand

April 22: First use of a chemical weapon , chlorine gas, near Ypres, Belgium

May 7: British ship Lusitania sunk by German U-boat

May 23: Italy enters war, against Austria-Hungary

October: Bulgaria joins war, on side of Central Powers

1916

Feb. 21: Battle of Verdun begins

March 9: Germany declares war on Portugal

July 1: Battle of the Somme begins, with first mass use of tanks

Aug. 27: Romania enters war, is invaded by Germany

THIRTY SEVEN OF ONE HUNDRED PHOTOS WORLD WAR ONE CENTENARY TIMELINE - In this undated file photo, an unidentified soldier, wearing a gas mask around his neck, bangs on a frying pan as a gas warning on the field near Reims, France. (AP Photo, File)
THIRTY SEVEN OF ONE HUNDRED PHOTOS WORLD WAR ONE CENTENARY TIMELINE - In this undated file photo, an unidentified soldier, wearing a gas mask around his neck, bangs on a frying pan as a gas warning on the field near Reims, France. (AP Photo, File) (AP)

Sept. 4: British take Dar es Salaam in German East Africa

October: Soldier Adolf Hitler wounded

Dec. 23: Allied forces defeat Turkish in Sinai Peninsula

1917

March: Baghdad falls to Anglo-Indian forces

April 6: United States declares war on Germany

April: Battle for Vimy Ridge , defining moment for Canada

July: Last Russian offensive ends in failure, as revolution nears; inconclusive Battle of Passchendaele in Belgium

Oct. 15: Spy Mata Hari executed by French firing squad

Oct. 26: Brazil declares war, joining Allied Powers

FILE - In this undated file photo American World War I soldiers wave their helmets after the Nov. 11, 1918 Armistice was signed in France. Hundreds of troops died on the final morning of World War I _ even after an armistice was reached and before it came into force. Death at literally the 11th hour highlighted the futility of a conflict that had become even more incomprehensible in four years of battle. (AP Photo, File)
FILE - In this undated file photo American World War I soldiers wave their helmets after the Nov. 11, 1918 Armistice was signed in France. Hundreds of troops died on the final morning of World War I _ even after an armistice was reached and before it came into force. Death at literally the 11th hour highlighted the futility of a conflict that had become even more incomprehensible in four years of battle. (AP Photo, File) (AP)

December: Battle of Jerusalem

1918

March 3: Treaty of Brest-Litovsk ends Russia's involvement in the war on the Eastern Front.

April 21: Legendary German fighter pilot known as the Red Baron shot down and killed near Amiens, France

June: Battle of Belleau Wood , defining moment for U.S. military

July 21: German submarine fires on Cape Cod, only attack on mainland U.S.

Sept. 26: Battle of the Meuse-Argonne begins

Oct. 30: Ottoman Empire signs armistice with Allies

Oct. 31: Dissolution of Austro-Hungarian Empire

Nov. 9: Germany's Kaiser Wilhelm II abdicates

WWI death toll compared with other modern conflicts
WWI death toll compared with other modern conflicts (AP)

Nov. 11: Germany signs armistice ending the war

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For more information on World War I, go to The Associated Press' WWI hub: https://www.apnews.com/WorldWarI

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World War I: An AP Centennial Commemorative Edition. Available now exclusively at Amazon: https://amzn.to/2JGrx5U