Political map of Europe & the Mediterranean 04 November 1915 (Central Power Breakthrough in the East): Italy joined the Allies (Allies of World War I) in May, but the rest of the year favored the Central Powers (Central Powers). In August the Germans pushed the Russians out of Poland (Gorlice–Tarnow Offensive), while in October the Bulgarians joined the War (World War I) and helped defeat Serbia (Serbian Campaign (World War I)). The  Allies landed in officially neutral Greece (Macedonian front (World War I)) in an attempt to save the Serbs, but were only able to rescue part of their fleeing army.