The failure of Serbia and Austrio-Hungary to be able to solve their problems without war was what led to the eventual declaration of war on Serbia by Austrio-Hungary. Normally, it would have been an ordinary war, but Serbia was allied to Russia, who was in turn allied too France and Britain, causing a domino effect in which each country successively declared war in an effort to show their support to their allies. This in turn turned what would have been a territorial war into a global war.
