The First World War, or the First World War (July 28, 1914 – November 11, 1918), also known as the Great War, was a global conflict between two coalitions: the Allies (or Entente) and the Central Powers. The main areas of conflict included Europe and the Middle East, as well as parts of Africa and the Asia-Pacific. The conflict saw significant developments in weapons such as tanks, aircraft, artillery, machine guns, and chemical weapons. One of the bloodiest conflicts in history, it resulted in approximately 30 million military casualties and 8 million civilian deaths from war-related causes and genocide. The movement of large numbers of people was a major factor in the deadly Spanish flu pandemic.
The causes of World War I included the rise of the German Empire and the decline of the Ottoman Empire, which disrupted the long-standing balance of power in Europe, exacerbated imperial rivalries, and triggered an arms race between the major powers. Rising tensions in the Balkans reached a peak on June 28, 1914, when Bosnian Serb Gavrilo Princip assassinated Franz Ferdinand, heir to the Austro-Hungarian throne. Austria-Hungary blamed Serbia and declared war on July 28. After Russia came to Serbia's defense, Germany declared war on Russia and France, who had formed an alliance. The United Kingdom joined the war after Germany invaded Belgium, and the Ottoman Empire joined the Central Powers in November. Germany's strategy in 1914 was to quickly defeat France and then send its army eastward. However, its advance was halted in September, and by the end of the year, the Western Front consisted of a nearly continuous line of trenches from the English Channel to Switzerland. The Eastern Front was more fortified, but despite costly offensives, neither side achieved significant gains. Italy, Bulgaria, Romania, Greece and other countries joined the war from 1915 onwards.
Major battles such as Verdun, the Somme, and Passchendaele failed to break the logjam on the Western Front. In April 1917, after Germany resumed unrestrained submarine warfare against Atlantic shipping, the United States joined the Allies. Later that year, the Bolsheviks seized power in Russia in the October Revolution; Soviet Russia signed an armistice with the Central Powers in December, followed by a separate peace treaty in March 1918. That month, Germany launched a Spring Offensive in the west, which, despite initial successes, exhausted and demoralized the German army. The Allied Hundred Days Offensive, which began in August 1918, led to the collapse of the German front line. Following the Vardar Offensive, Bulgaria signed an armistice in late September. By early November, the Allies had signed armistices with the Ottomans and Austria-Hungary, leaving Germany isolated. Facing revolution at home, Kaiser Wilhelm II abdicated on November 9, and the war ended with the Armistice of November 11, 1918.
The Paris Peace Conference of 1919-1920 imposed compromises on the defeated powers. Under the Treaty of Versailles, Germany lost considerable territory, was stripped of its weapons, and was required to pay substantial war reparations to the Allies. The collapse of the Russian, German, Austro-Hungarian, and Ottoman empires created new national boundaries and led to the creation of newly independent countries such as Poland, Finland, the Baltic countries, Czechoslovakia, and Yugoslavia. The League of Nations was established to maintain world peace, but its failure to manage the instability of the interwar period contributed to the outbreak of World War II in 1939.
Before World War II, the events of 1914–1918 were commonly referred to as the Great War or simply the World War. In August 1914, The Independent said of the conflict, "This is the Great War. It deserves its own name." Ten years after its end, many expected it to be "the war to end all wars" because of its immense destruction and high death toll. The term First World War was first used in September 1914, when German biologist and philosopher Ernst Haeckel wrote that the ongoing "European War" would become "the first world war in the full sense of the word."
Background of the war
Political and Military Alliances
For most of the 19th century, the major European powers maintained a tenuous balance of power known as the Concert of Europe. After 1848, this was challenged by Britain's descent into splendid isolation, the decline of the Ottoman Empire, New Imperialism, and the rise of Prussia under Otto von Bismarck. Victory in the Franco-Prussian War of 1870–1871 allowed Bismarck to consolidate a German Empire. After 1871, French policy aimed to avenge this defeat and expand France's colonial empire.
In 1873, Bismarck negotiated the League of the Three Emperors, comprising Austria-Hungary, Russia, and Germany. After the Russo-Turkish War of 1877–1878, the League was dissolved due to Austrian concerns about growing Russian influence in the Balkans, an area they considered of vital strategic interest. Germany and Austria-Hungary formed the Dual Alliance in 1879, which became the Triple Alliance when Italy joined in 1882. For Bismarck, the purpose of these agreements was to isolate France so that the three empires could resolve any disputes among themselves. In 1887, Bismarck created the Reinsurance Treaty, a secret agreement between Germany and Russia that would remain neutral if either France or Austria-Hungary were attacked.
For Bismarck, peace with Russia was the foundation of German foreign policy, but in 1890, Wilhelm II forced him to retire. The latter was persuaded by his new Chancellor, Leo von Caprivi, not to renew the Reinsurance Treaty. This led France to agree to the Franco-Russian Alliance in 1894, followed by the Entente Cordiale with Britain in 1904. The Triple Entente was completed by the Anglo-Russian Convention of 1907. Although these were not formal alliances, by resolving long-standing colonial disputes in Asia and Africa, British support for either France or Russia in any future conflict became a possibility. This was further exacerbated by British and Russian support for France against Germany during the Agadir Crisis of 1911.
Germany's economic and industrial power continued to grow rapidly after 1871. With the support of Wilhelm II, Admiral Alfred von Tirpitz used this growth to build an Imperial German Navy that could rival the British Royal Navy. This policy was based on the work of US naval author Alfred Thayer Mahan, who argued that a blue-water navy was essential to projecting power worldwide; Tirpitz had his books translated into German, while Wilhelm made them mandatory reading for his advisors and senior military staff.
Bismarck opposed any attempt to compete with the Royal Navy, believing that Britain would not interfere in Europe as long as its maritime dominance was secure. His removal in 1890 led to a change in policy and an arms race between the Anglo-German navies. Despite the enormous sums spent by Tirpitz, the launch of HMS Dreadnought in 1906 rendered every existing battleship obsolete, giving the British a technological advantage they never relinquished. Ultimately, Germany invested enormous resources in building a navy large enough to trouble Britain, but could not defeat it. In 1911, Chancellor Theobald von Bethmann-Hollweg conceded defeat, leading to the Rüstungswende, or 'turning point on armaments,' when he shifted spending from the navy to the army.
This decision was driven by German concerns about the speed of Russia's recovery following its defeat in the Russo-Japanese War and the subsequent Russian Revolution of 1905. Economic reforms led to a significant expansion of railway and transportation infrastructure after 1908, especially along its western border. Since Germany and Austria-Hungary relied on rapid mobilization to compensate for their numerical weakness compared to Russia, the threat posed by closing this gap was more important than confronting the Royal Navy. In 1913, Germany increased its standing army by 170,000 men, followed by France's extension of compulsory military service from two to three years, prompting similar measures from the Balkan countries, Italy, the Ottoman Empire, and Austria-Hungary. Accurate figures are difficult to calculate due to differences in expenditure categories, which often exclude civilian infrastructure projects, such as railways, which had logistical significance and military applications. However, from 1908 to 1913, military expenditures for the six major European powers actually increased by more than 50%.
Conflict in the Balkans
In the years leading up to 1914, the Balkan region faced numerous crises as other powers sought to capitalize on the decline of the Ottoman Empire. Pan-Slavic and Orthodox Russia viewed itself as the protector of Serbia and other Slavic nations, yet it also desired that the strategically vital Bosphorus Strait remain under the control of a weak Ottoman government rather than an ambitious Slavic power like Bulgaria. Russia had its sights set on northeastern Anatolia, while the claims of its Balkan allies frequently clashed with one another. These conflicting interests divided Russian policymakers and further exacerbated instability in the region.
Austrian leaders believed that the Balkan region was essential for the survival of their empire and viewed Serbian expansion as a direct threat. The Bosnian Crisis of 1908–1909 began when Austria annexed the former Ottoman territories of Bosnia and Herzegovina—which it had occupied since 1878—into its empire. Although European powers condemned this unilateral move—which coincided with Bulgaria's declaration of independence from the Ottoman Empire—they ultimately accepted it, as no consensus could be reached on how to resolve the situation. Some historians view this as a critical escalation of tensions that eliminated any possibility of cooperation between Austria and Russia in the Balkans and also damaged diplomatic relations with Serbia and Italy.
Tensions escalated after the Ottoman Empire's weakness was exposed during the Italo-Turkish War (1911–1912) and the formation of the 'Balkan League'—an alliance comprising Serbia, Bulgaria, Montenegro, and Greece. During the First Balkan War (1912–1913), the League rapidly seized most of the Ottoman Empire's territories in the Balkans, taking outside observers by surprise. Austria began partial military mobilization after Serbia occupied Adriatic ports; this process commenced on November 21, 1912, and included troops stationed along the Russian border in Galicia. In response, the Russian government decided against mobilizing its own forces, as it did not wish to trigger a war.
In 1913, the Great Powers attempted to reassert their control through the Treaty of London. This treaty established an independent Albania and expanded the territories of Bulgaria, Serbia, Montenegro, and Greece. However, disputes among the victors triggered the Second Balkan War—a conflict lasting 33 days—when Bulgaria attacked Serbia and Greece on June 16, 1913; Bulgaria was defeated and forced to cede most of Macedonia to Serbia and Greece, and Southern Dobruja to Romania. Consequently, even countries like Serbia and Greece, which had benefited from the Balkan Wars, felt they had not received their "just due." Meanwhile, it became clear to Austria just how indifferent other powers, including Germany, were to its concerns. This mix of resentment, nationalism, and insecurity helps explain why the Balkans came to be known as the "powder keg of Europe" in the period leading up to 1914.
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