The murder of Archduke Franz Ferdinand, he was going to take the throne for the Austria-Hungarian empire. Then the black hand killed him and boom of war alliance broke out. Austria had Italy(cross sides later), Germany and Ottomans. They attack Serbia, where the black hand is from. Russia comes in to help out. France is there all so they join. Germany wants to attack France. But they have a real good defense. So they go through Belgium, turns out they have a good army and make the brits mad and they join the war. Eventually this nation is allied with that nations and everyone joins in.