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.
Foreign involvement in the Spanish Civil War The Spanish Civil War had large numbers of non-Spanish citizens participating in combat and advisory positions. The governments of Germany, Italy—and to a lesser extent Portugal—contributed money, munitions, manpower and support to Nationalist forces led by Francisco Franco. The government of the Soviet Union, and to a lesser extent France and Mexico, likewise aided the Republicans (Loyalists) of the Second Spanish Republic. The aid came even after all the European powers had signed a Non-Intervention Agreement in 1936. While individual sympathy for the plight of the Spanish Republic was widespread in the liberal democracies, pacifism and the fear of another world war prevented them from selling or giving arms. The Nationalist pleas meanwhile were answered within days by Hitler and Mussolini.