World War I Fast Facts

CNN Editorial Research
Updated 8:33 AM EDT, Thu July 14, 2022
World War I ushered in an era of chemical weapons use that lingers, lethally, into the present day. About 1 million casualties were inflicted, and 90,000 were killed. Here, French troops wear an early form of gas mask in the trenches during the first widespread use of gas, by the Germans at the Second Battle of Ypres in 1916.
Chemical weapons in World War I —
World War I ushered in an era of chemical weapons use that lingers, lethally, into the present day. About 1 million casualties were inflicted, and 90,000 were killed. Here, French troops wear an early form of gas mask in the trenches during the first widespread use of gas, by the Germans at the Second Battle of Ypres in 1916.
Hulton Archive/Getty Images
French soldiers making a gas and flame attack on German trenches in Flanders, Belgium, in 1918. German forces were the first to open valves on gas cylinders, releasing the toxic cloud on unprepared French troops in Ypres in 1915.
Chemical weapons in World War I —
French soldiers making a gas and flame attack on German trenches in Flanders, Belgium, in 1918. German forces were the first to open valves on gas cylinders, releasing the toxic cloud on unprepared French troops in Ypres in 1915.
DOD/Signal Office/Getty Images
The bodies of hundreds of Italian soldiers are strewn across the battlefield, victims of a gas and flame attack during World War I, as others haul the wounded on stretchers. They were members of the Ninth Italian Regiment of the Queen's Brigade.
Chemical weapons in World War I —
The bodies of hundreds of Italian soldiers are strewn across the battlefield, victims of a gas and flame attack during World War I, as others haul the wounded on stretchers. They were members of the Ninth Italian Regiment of the Queen's Brigade.
Hulton Archive/Getty Images
Early gas masks were often ineffectual. The Germans and Americans would ultimately be the most successful in creating barriers to lethal gases. A German soldier shows how to wear one version.
Chemical weapons in World War I —
Early gas masks were often ineffectual. The Germans and Americans would ultimately be the most successful in creating barriers to lethal gases. A German soldier shows how to wear one version.
Bain News Service/Getty Images
A soldier demonstrates an ungainly French gas mask. "French masks were notoriously unreliable,"<a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2376985/" target="_blank" target="_blank"> wrote</a> historian Gerald Fitzgerald.
Chemical weapons in World War I —
A soldier demonstrates an ungainly French gas mask. "French masks were notoriously unreliable," wrote historian Gerald Fitzgerald.
Mondadori Portfolio/Getty Images
A German cavalry unit with both horses and soldiers wearing gas masks advances during the Second Battle of the Aisne at Soissons, France, in June 1918.
Chemical weapons in World War I —
A German cavalry unit with both horses and soldiers wearing gas masks advances during the Second Battle of the Aisne at Soissons, France, in June 1918.
Mondadori Portfolio/Getty Images
A German soldier wears a more rudimentary gas mask in 1915. Although the Germans were first to deploy chemical weapons in the war, both sides were soon routinely using chlorine and other gases in battle.
Chemical weapons in World War I —
A German soldier wears a more rudimentary gas mask in 1915. Although the Germans were first to deploy chemical weapons in the war, both sides were soon routinely using chlorine and other gases in battle.
Bain News Service/Getty Images
Men of the British Army's 55th Division, blinded by a poison gas attack, in April 1918. British soldier Wilfred Owen captured the panic of an attack in verse "Gas! Gas! Quick, boys! -- An ecstasy of fumbling, Fitting the clumsy helmets just in time; But someone still was yelling out and stumbling, And flound'ring like a man on fire or lime."
Chemical weapons in World War I —
Men of the British Army's 55th Division, blinded by a poison gas attack, in April 1918. British soldier Wilfred Owen captured the panic of an attack in verse "Gas! Gas! Quick, boys! -- An ecstasy of fumbling, Fitting the clumsy helmets just in time; But someone still was yelling out and stumbling, And flound'ring like a man on fire or lime."
Universal History Archive/Getty Images
CNN  — 

Here’s some background information about World War I, also known as the First World War and the Great War, which lasted from 1914 to 1918.

Causes of World War I

The assassination of Archduke Franz Ferdinand of Austria-Hungary by Gavrilo Princip, a Bosnian Serb, led to Austria-Hungary declaring war on Serbia.

The Central Powers consisted of Austria-Hungary, Bulgaria, Germany and the Ottoman Empire (now Turkey).

The Allied Powers consisted of Belgium, France, Great Britain, Greece, Italy, Montenegro, Portugal, Romania, Russia, Serbia and the United States.

The United States declared neutrality until German submarine warfare threatened American commercial shipping.

US Troop Statistics

(Source: Defense Casualty Analysis System)
Battle deaths: 53,402
Non-battle deaths: 63,114
Total deaths: 116,516
Total US soldiers wounded: 204,002
Total number of US troops that served in the conflict: 4,734,991

Other Military Casualties by Country

(Source: Encyclopedia Britannica)
Austria-Hungary: 1,200,000 dead; 3,620,000 wounded
Belgium: 13,716 dead; 44,686 wounded
Bulgaria: 87,500 dead; 152,390 wounded
France: 1,357,800 dead; 4,266,000 wounded
Germany: 1,773,700 dead; 4,216,058 wounded
Great Britain: 908,371 dead; 2,090,212 wounded
Greece: 5,000 dead; 21,000 wounded
Italy: 650,000 dead; 947,000 wounded
Japan: 300 dead; 907 wounded
Montenegro: 3,000 dead; 10,000 wounded
Ottoman Empire (Turkey): 325,000 dead; 400,000 wounded
Portugal: 7,222 dead; 13,751 wounded
Romania: 335,706 dead; 120,000 wounded
Russia: 1,700,000 dead; 4,950,000 wounded
Serbia: 45,000 dead; 133,148 wounded
Grand Total (including US): 8,528,831 dead; 21,189,154 wounded

Timeline

June 28, 1914 - Gavrilo Princip, who has ties to the Serbian terrorist-type group the Black Hand, assassinates Archduke Franz Ferdinand of Austria-Hungary.

July 28, 1914 - Austria-Hungary declares war on Serbia.

August 1, 1914 - Germany declares war on Russia.

August 2, 1914 - Ottoman Empire and Germany sign a secret treaty of alliance.

August 4, 1914 - Germany invades Belgium. President Woodrow Wilson declares that the United States is neutral. Britain declares war on Germany.

August 10, 1914 - Austria-Hungary invades Russia, opening the fighting on the Eastern Front.

August 26-30, 1914 - Battle of Tannenberg, Prussia.

September 12, 1914 - First battle of the Aisne in France begins, marking the beginning of trench warfare.

November 3, 1914 - Russia declares war on the Ottoman Empire.

November 5, 1914 - Great Britain and France declare war on the Ottoman Empire.

April 22-May 25, 1915 - Second Battle of Ypres, marking the first wide-scale use of poison gas by Germany.

May 7, 1915 - A German U-20 submarine sinks the British passenger ship, the Lusitania; 1,198 are killed, including 128 Americans.

June 1915-November 1917 - Battles of the Isonzo, Italy.

1915 - Battle of Krithia, Gallipoli peninsula, Ottoman Empire.

February 21-July 1916 - Battle of Verdun, France, the war’s longest battle, with almost a million casualties.

May 31-June 1, 1916 - Battle of Jutland, North Sea near Denmark - a sea battle between British and German navies.

July 1, 1916-November 1916 - First Battle of the Somme River, France. The British introduce the tank.

April 6, 1917 - The United States declares war against Germany after the interception and publication of the Zimmermann Telegram and the sinking of three US merchant ships by German U-boats.

June 26, 1917 - American troops begin landing in France.

November 20, 1917 - Battle of Cambrai, France.

December 3, 1917 - Russia signs an armistice with Germany.

March 3, 1918 - Russia signs the Treaty of Brest-Litovsk, ending hostilities with the Central Powers and withdrawing Russia from this war.

March 21-April 5, 1918 - Second Battle of the Somme River.

September 29, 1918 - Bulgaria signs an armistice.

October 30, 1918 - Ottoman Empire signs an armistice.

November 3, 1918 - Austria-Hungary signs an armistice.

November 11, 1918 - Germany accepts the armistice terms demanded by the Allies, ending the war.

June 28, 1919 - The Treaty of Versailles is signed at the Palace of Versailles, France.

November 11, 2018 - Ceremonies take place around the world to mark 100 years to the day since the armistice that saw the end of World War I. French President Emmanuel Macron leads the international Armistice Day commemorations by the Tomb of the Unknown Soldier, which lies at the foot of the Arc de Triomphe monument in Paris. US President Donald Trump and first lady Melania Trump are among those in Paris for the commemorations, which coincide with Veterans Day in the United States.