In case of what country's attack was the origins of the Central Powers?
Central Powers The Central Powers (German: "Mittelmächte" ; Hungarian: "Központi hatalmak" ; Turkish: "İttifak Devletleri" or "Bağlaşma Devletleri" ; Bulgarian: Централни сили "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.
Macedonian Front The Macedonian Front of World War I, also known as the Salonica Front (after Thessaloniki), was formed as a result of an attempt by the Allied Powers to aid Serbia, in the fall of 1915, against the combined attack of Germany, Austria-Hungary and Bulgaria. The expedition came too late and in insufficient force to prevent the fall of Serbia, and was complicated by the internal political crisis in Greece (the "National Schism"). Eventually, a stable front was established, running from the Albanian Adriatic coast to the Struma River, pitting a multinational Allied force against the Bulgarian Army, which was at various times bolstered with smaller units from the other Central Powers. The Macedonian Front remained quite stable, despite local actions, until the great Allied offensive in September 1918, which resulted in the capitulation of Bulgaria and the liberation of Serbia.