The Dual Alliance (German: Zweibund, Hungarian: Kettős Szövetség) was a defensive alliance between Germany and Austria-Hungary, which was created by treaty on October 7, 1879, as part of Germany's Otto von Bismarck's system of alliances to prevent or limit war.^[1] The two powers promised each other support in case of attack by Russia. Also, each state promised benevolent neutrality to the other if one of them was attacked by another European power (generally taken to be France, even more so after the Franco-Russian Alliance of 1894). Bismarck saw the alliance as a way to prevent the isolation of the German Empire, which had just been founded a few years before, and to preserve peace, as Russia would not wage war against both empires.^[2][3]

Events leading to World War I
Unification of Germany 1866–1871 Franco-Prussian War 1870–1871 Second Concert of Europe 1871 Great Eastern Crisis 1875–1878 Campaign in Bosnia 1878 Dual Alliance 1879 Boer Wars 1880–1902 Austro–Serbian Alliance 1881–1903 Triple Alliance 1882 Berlin Conference 1884 Bulgarian Crisis 1885–1888 Reinsurance Treaty 1887–1890 Franco-Russian Alliance 1894 Anglo-German naval arms race 1898–1912 Fashoda incident 1898 Anglo-Japanese Alliance 1902 Russo-Japanese War 1904–1905 Entente Cordiale 1904 First Moroccan Crisis 1905–1906 Pig War 1906–1908 Anglo-Russian Convention 1907 Young Turk Revolution 1908 Bosnian Crisis 1908–1909 Racconigi Bargain 1909 Second Moroccan Crisis 1911 Italo-Turkish War 1911–1912 Balkan Wars 1912–1913 Assassination of Franz Ferdinand 1914 July Crisis 1914
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Formation

When Austria-Hungary and Germany formed an alliance in 1879, it was one of the more surprising alliances of its time.^{[citation needed]} Though both shared the German language and a similar culture, Austria-Hungary and Germany were often driven apart, most notably during the recent Austro-Prussian War. Additionally, the Habsburg rulers believed that the promotion of nationalism, which was favoured by Germany, would destroy their multinational empire. However, their common distrust of Russia brought both empires together for a common cause.^[4]

Alliance against Russia

After the formation of the German Empire in 1871, German Chancellor Otto von Bismarck wanted to portray his nation as a peacemaker and preserver of the European status quo, to gain more power for the German Empire and to unify Germany. In 1878, the Russian Empire defeated the Ottoman Empire in the Russo-Turkish War. The resulting Treaty of San Stefano gave Russia considerable influence in the Balkans, a development that outraged Austria-Hungary, Russia's chief rival in the Balkan region (despite being an ally of the Russians and the Germans in the League of the Three Emperors). Hence, in 1878, Bismarck called an international conference (the Congress of Berlin) to sort out the problem. The Treaty of Berlin that resulted from the conference reversed Russia's gains from the Treaty of San Stefano and provided the Austrians with compensation in the form of Bosnia. Despite Bismarck's attempts to play the role of an "honest broker" at the Congress of Berlin, Russo-German relations deteriorated following the conference. The Three Emperors' League was discontinued, and Germany and Austria-Hungary were free to ally against Russia.^[5]

Italy joins alliance

In 1881, Italy lost in the competition with France to establish a colony in Tunis (now Tunisia). To enlist diplomatic support, Italy joined Germany and Austria-Hungary to form the Triple Alliance in 1882, which was the first formal alliance in Europe, the second being the Triple Entente, an informal alliance, formed in 1907.

During World War I, however, Italy did not go to war immediately with its allies but stayed neutral. In 1915, it joined the Entente powers and declared war on Austria-Hungary and, in 1916, against Germany. The Dual Alliance persisted throughout the war, known as the Central Powers, and ended by their defeat in 1918.