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1914
July 28 - Austria-Hungary declares war on Serbia, marking the start of World War I.
August: Germany declares war on Russia and France and invades Belgium.
August 4 - Britain declares war on Germany, turning World War I into a global conflict.
September 5 - The Battle of the Marne begins and the Germans are repelled. -
1915
22 April: The Germans use poison gas as a chemical weapon for the first time in the Flanders region.
May 7: The German submarine Lusitania is sunk, prompting international condemnation. -
1916
July 1 - The Battle of the Somme begins, becoming one of the bloodiest battles of the First World War.
23 July: The Germans use poison gas in the Battle of Verdun. -
1917
The United States entered World War I and declared war on Germany.
The February and October Revolutions in Russia led to the end of tsarism and the establishment of Soviet power. -
1918
November 11 - World War I ends with the surrender of Germany. -
1919
The Paris Peace Conference was convened to deal with the aftermath of the war and establish a new international order. -
1920
The economy was booming, jazz was popular, and the film and fashion industries were booming.
The social atmosphere is more open, and the status of women is gradually improving. -
1929
The stock market crashed, triggering a global depression. -
1930
As the Great Depression continued, governments around the world responded with different measures.
The international situation was tense and fascism was on the rise in Europe and parts of Asia. -
1939
September 1 - Germany invades Poland and World War II begins -
1940
Germany won major victories in Western Europe, including the occupation of most of France.
Britain successfully defended itself against German air attacks in the Battle of Britain.