World
War I (WWI) was a global war centred in Europe that began on 28 July
1914 and lasted until 11 November 1918. It was predominantly called the
World War or the Great War from its occurrence until the start of World
War II in 1939, and the First World War or World War I thereafter. It
involved all the world's great powers,[5] which were assembled in two
opposing alliances: the Allies (based on the Triple Entente of the
United Kingdom, France and Russia) and the Central Powers (originally
the Triple Alliance of Germany, Austria-Hungary and Italy; but, as
Austria–Hungary had taken the offensive against the agreement, Italy did
not enter into the war).[6] These alliances were both reorganised and
expanded as more nations entered the war: Italy, Japan and the United
States joined the Allies, and the Ottoman Empire and Bulgaria the
Central Powers. Ultimately, more than 70 million military personnel,
including 60 million Europeans, were mobilised in one of the largest
wars in history.[7][8] More than 9 million combatants were killed,
largely because of technological advancements that led to enormous
increases in the lethality of weapons without corresponding improvements
in protection or mobility. It was the sixth-deadliest conflict in world
history, subsequently paving the way for various political changes,
such as revolutions in many of the nations involved.[9]
One of the
long-term causes of the war was the resurgence of imperialism in the
foreign policies of the great powers of Europe. More immediately, the
assassination of Archduke Franz Ferdinand of Austria, the heir to the
throne of Austria-Hungary, on 28 June 1914 by Yugoslav nationalist
Gavrilo Princip in Sarajevo triggered a diplomatic crisis when
Austria-Hungary subsequently delivered an ultimatum to the Kingdom of
Serbia.[10][11] Several alliances formed over the previous decades were
invoked. Within weeks, the major powers were at war; via their colonies,
the conflict soon spread around the world.
On 28 July, the
Austro-Hungarians fired the first shots of the war as preparation for
the invasion of Serbia.[12][13] While the Russians mobilised, the
Germans invaded neutral Belgium and Luxembourg on the way to France,
providing a casus belli for Britain's declaration of war against
Germany. After the German march on Paris was brought to a halt—the
so-called Miracle of the Marne—the Western Front settled into a static
battle of attrition with a trench line that changed little until 1917.
On the Eastern Front, the Russian army was successful against the
Austro-Hungarians, but was stopped in its invasion of East Prussia by
the Germans. In November the Ottoman Empire joined the war, opening up
fronts in the Caucasus, Mesopotamia and the Sinai. Italy and Bulgaria
went to war in 1915 and Romania in 1916. In Russia, the tsar's
government collapsed in March 1917 and a subsequent revolution in
November brought the Russians to terms with the Central Powers. After a
1918 German offensive along the western front, the Allies drove back the
Germans in a series of successful offensives and American forces began
entering the trenches. Germany, which had its own trouble with
revolutionaries, agreed to an armistice on 11 November 1918. The war
ended in victory for the Allies.
Events on the home fronts were as
tumultuous as on the battle fronts, as the participants tried to
mobilize their manpower and economic resources to fight a total war. By
the end of the war, four major imperial powers—the German, Russian,
Austro-Hungarian and Ottoman empires—ceased to exist. The successor
states of the former two lost a great amount of territory, while the
latter two were dismantled entirely. The map of central Europe was
redrawn into several smaller states.[14] The League of Nations was
formed in the hope of preventing another such conflict. The European
nationalism spawned by the war and the breakup of empires, the
repercussions of Germany's defeat and problems with the Treaty of
Versailles are agreed to be factors contributing to World War II