The Central Powers (German: Mittelmächte; Hungarian: Központi hatalmak; Turkish: İttifak Devletleri / Bağlaşma Devletleri; Bulgarian: Централни сили, translit. Tsentralni sili), consisting of Germany, Austria-Hungary, the Ottoman Empire and Bulgaria – hence also known as the Quadruple Alliance (German: Vierbund) – was one of the two main factions during World War I (1914–18). It faced and was defeated by the Allied Powers that had formed around the Triple Entente. The Powers' origin was the alliance of Germany and Austria-Hungary in 1879. The Ottoman Empire and Bulgaria did not join until after World War I had begun, although the Ottoman Empire retained close relations with both Germany and Austria-Hungary since the beginning of the 20th century.
The Central Powers consisted of the German Empire and the Austro-Hungarian Empire at the beginning of the war. The Ottoman Empire joined the Central Powers later in 1914. In 1915, the Kingdom of Bulgaria joined the alliance. The name "Central Powers" is derived from the location of these countries; all four (including the other groups that supported them except for Finland and Lithuania) were located between the Russian Empire in the east and France and the United Kingdom in the west. Finland, Azerbaijan, and Lithuania joined them in 1918 before the war ended and after the Russian Empire collapsed.
The Central Powers were composed of the following nations:
In early July 1914, in the aftermath of the assassination of Austro-Hungarian Archduke Franz Ferdinand and the immediate likelihood of war between Austria-Hungary and Serbia, Kaiser Wilhelm II and the German government informed the Austro-Hungarian government that Germany would uphold its alliance with Austria-Hungary and defend it from possible Russian intervention if a war between Austria-Hungary and Serbia took place. When Russia enacted a general mobilization, Germany viewed the act as provocative. The Russian government promised Germany that its general mobilization did not mean preparation for war with Germany but was a reaction to the events between Austria-Hungary and Serbia. The German government regarded the Russian promise of no war with Germany to be nonsense in light of its general mobilization, and Germany, in turn, mobilized for war. On 1 August, Germany sent an ultimatum to Russia stating that since both Germany and Russia were in a state of military mobilization, an effective state of war existed between the two countries. Later that day, France, an ally of Russia, declared a state of general mobilization.
In August 1914, Germany waged war on Russia, the German government justified military action against Russia as necessary because of Russian aggression as demonstrated by the mobilization of the Russian army that had resulted in Germany mobilizing in response.
After Germany declared war on Russia, France with its alliance with Russia prepared a general mobilization in expectation of war. On 3 August 1914, Germany responded to this action by declaring war on France. Germany, facing a two-front war, enacted what was known as the Schlieffen Plan, that involved German armed forces needing to move through Belgium and swing south into France and towards the French capital of Paris. This plan was hoped to quickly gain victory against the French and allow German forces to concentrate on the Eastern Front. Belgium was a neutral country and would not accept German forces crossing its territory. Germany disregarded Belgian neutrality and invaded the country to launch an offensive towards Paris. This caused Great Britain to declare war against the German Empire, as the action violated the Treaty of London that both nations signed in 1839 guaranteeing Belgian neutrality and defense of the kingdom if a nation reneged.
Subsequently, several states declared war on Germany in late August 1914, with Italy declaring war on Austria-Hungary in 1915 and Germany on 27 August 1916, the United States declaring war on Germany on 6 April 1917 and Greece declaring war on Germany in July 1917.