In the years leading up to World War I, there were two primary allied camps in Europe: Austria-Hungary, Germany, and Italy had a long-standing alliance; Russia, France, and Great Britain shared another defensive alliance. These alliances were intended to deter aggression. Instead, they were one of the leading causes of the war.
Secrecy was one component of these alliances. They were often formed clandestinely, to be revealed later, when conflict rose between nations and powerful friends were useful. Fear was another component. France and Russia, fearing the growing influence and global ambitions of Germany, formed an alliance. In response, Germany strengthened its ties with the Austria-Hungarian Empire. Then Great Britain allied with France and Russia, seeking to maintain a balance of power in Europe against Germany's increasing might. Faced with a growing bloc of opposition to its vision of world dominance, Germany feared its window of opportunity was closing. However, in 1914 a conflict between Russia and Austria-Hungary would keep that window open. At the same time, it would test the loyalty and military strength of these alliances.
On June 28, 1914, Gavrilo Princip, a Bosnian Serb recruited by the covert terrorist society the Black Hand, assassinated Archduke Franz Ferdinand of Austria and his wife, Sophie, during their visit to Sarajevo, Bosnia. Austria-Hungary subsequently declared war on Serbia. Russia had close ties to Serbia, and Austria-Hungary called on Germany to help deter Russia from becoming involved in the conflict. Germany subsequently called on France to remain neutral, a call France would not heed. Russia and France mobilized troops in response to the Austrian attack on Serbia. Standing with Austria, Germany demanded that Belgium allow German troops safe passage through their country, which at the time was neutral. Great Britain was allied with Belgium and declared war on Germany when German troops invaded Belgium. This entire chain reaction of events is often referred to by historians as the July Crisis.Soon, much of the continent was at war. At first the war was popular with many Europeans. They were confident it would be short, with each side certain of victory. A wave of nationalism, or excessive pride in one's county, swept across Europe. What followed was a drawn-out conflict that would become the deadliest in human history. Approximately 8.5 million soldiers died in World War I, which has been called the Great War. Even larger numbers of civilians were killed. The plight of the World War I soldier has been captured with frank and painful realism in Erich Maria Remarque's 1929 novel All Quiet on the Western Front.