Italy: To proud to fight until the spring of 1915 (Sacred Egoism). Entered the war after the break down of the Schieffen/Moltke Plan and the Miracle at the Marne. Italy feared the war would end before they could get in on the future peace treaty.
Britain welcomed Italy with open arms going as far as to pressure Russia because Serbia (Russia's friend) wanted the same land Italy wanted (Though the Allies had no intention of Italy what he was promised). Italy feared a nationalistic Serbic country. Also wanted dominance in the Adriatic sea via the Dalmatian coast. Woodrow Wilson ruined this stuff for Italy so Italy hated him some WW.
Serbia and Austria-HungaryAustria-Hungary wanted to control and destroy Serbia because they saw Serbia as a cancer that would kill them.
The Austria-Hungarians attacked Serbia Aug. 16-19 (the Battle of Cer). Serbia kicked Austria-Hungary's ass and Austria-Hungary evacuated Serbia humiliated. Austria-Hungary regroups in late 1914, but Serbia once again beats back Austria-Hungary in the battle of Kolubara River.
Austria-Hungary launched an offensive late 1915. Serbia fell because of the massive number of casualties (1 million people) because 6 out of 10 men in Serbia died in the war.
Even though Bulgaria was Slavic like Russia, Russia had no chance with Bulgaria so Germany made friends with Bulgaria. Germany and Bulgaria entered into a Treaty of Amity and Alliance. This was a defensive military alliance between Germany and Bulgaria. Bulgaria was secretly promised half of Serbia. Bulgaria equipped them-self well and expelled the Allies from Serbia alone.
"System of extermination"