World War I (WWI) was a global war centered 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, 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). These alliances both reorganized (Italy fought for the Allies) and expanded as more nations entered the war. Ultimately, more than 70 million military personnel, including 60 million Europeans, were mobilized in one of the largest wars in history. 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. Long-term causes of the war included the imperialistic foreign policies of the great powers of Europe, including the German Empire, the Austro-Hungarian Empire, the Ottoman Empire, the Russian Empire, the British Empire, the French Republic, and Italy.
In the 19th century, the major European powers had gone to great lengths to maintain a balance of power throughout Europe, resulting in the existence of a complex network of political and military alliances throughout the continent by 1900. These had started in 1815, with the Holy Alliance between Prussia, Russia, and Austria. Then, in October 1873, German Chancellor Bismarck negotiated the League of the Three Emperors (German: Dreikaiserbund) between the monarchs of Austria–Hungary, Russia and Germany. This agreement failed because Austria–Hungary and Russia could not agree over Balkan policy, leaving Germany and Austria–Hungary in an alliance formed in 1879, called the Dual Alliance. This was seen as a method of countering Russian influence in the Balkans as the Ottoman Empire continued to weaken. In 1882, this alliance was expanded to include Italy in what became the Triple Alliance.
When Wilhelm II ascended to the throne as German Emperor (Kaiser), Bismarck was compelled to retire and his system of alliances was gradually de-emphasised.
Two years later, the Franco-Russian Alliance was signed to counteract the force of the Triple Alliance.
In 1904, the United Kingdom signed a series of agreements with France, the Entente Cordiale, and in 1907, the United Kingdom and Russia signed the Anglo-Russian Convention.
While these agreements did not formally ally the United Kingdom with France or Russia, they made British entry into any future conflict involving France or Russia probable, and the system of interlocking bilateral agreements became known as the Triple Entente.
HMS Dreadnought. A naval arms race existed between the United Kingdom and Germany.
German industrial and economic power had grown greatly after unification and the foundation of the Empire in 1871. With the launch of HMS Dreadnought in 1906, the British Empire expanded on its significant advantage over its German rival. The arms race between Britain and Germany eventually extended to the rest of Europe, with all the major powers devoting their industrial base to producing the equipment and weapons necessary for a pan-European conflict. Between 1908 and 1913, the military spending of the European powers increased by 50 percent. In 1912 and 1913, the First Balkan War was fought between the Balkan League and the fracturing Ottoman Empire. The...