In case of what country's attack was the origins of the Central Powers?
Dual Alliance (1879) The Dual Alliance was a defensive alliance between Germany and Austria-Hungary, which was created by treaty on 7 October 1879 as part of Bismarck's system of alliances to prevent or limit war. 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). Germany’s Otto von Bismarck saw the alliance as a way to prevent the isolation of Germany and to preserve peace, as Russia would not wage war against both empires.
Berlin Memorandum The Berlin Memorandum was a document drawn up by the three imperial world powers in 1876 to address the Eastern Question during the Crisis of 1875-1878. The purpose of the Berlin Memorandum was for the three imperial powers of Russia, Austria-Hungary, and Germany to address the state of relations between the Islamic Ottoman Empire and with the Christian peoples of the Balkans, with whom these imperial powers had international relationships and interests, and to correct the "Andrássy Note", a document that preceded the Berlin Memorandum and had similar intentions in creating an armistice and plan of reforms for the Balkans and the Ottoman Empire.