On June 28, 1914, a young man of Serbian descent named Gavrilo Princip assassinated Archduke Franz Ferdinand, heir to the Austro-Hungarian Empire, in Sarajevo, Bosnia. The shooting triggered the terms of one alliance after another, bringing in nearly every European power and setting in motion their long-standing, rigid war plans. Aggressive posturing by national leaders and widespread public support for war quickly escalated the situation into a continent-wide conflict.
The assassin Princip was part of a Bosnian Serb independence movement. Austria-Hungary blamed Serbia for the shooting, but knew that Russia would support its fellow Slavic nation. First it secured Germany’s backing in case Russia intervened, and then it issued a series of demands to the Serbian government.
Germany’s involvement escalated the situation to a continent-wide crisis. Germany assumed the alliance between France and Russia would force it to fight on two battlefronts. Its war plan (the Schlieffen Plan) therefore called for an overwhelming invasion to quickly defeat France before turning to deal with Russia’s massive but slow-moving army. In order to strike France, Germany had to go through Belgium, which would bring in Britain to defend Belgium’s neutrality.
Although Serbia accepted nearly all of Austria-Hungary’s demands, Austria-Hungary declared war on July 28.As the crisis deepened, other nations activated their war plans. Huge crowds in cities across Europe demonstrated broad public support for war. The war plans took on a life of their own, despite the efforts of diplomats and even after a change of heart by Germany’s Kaiser Wilhelm. Military leaders insisted that the forward momentum of millions of troops and thousands of tons of supplies could not be halted.
On August 1, after Russia moved to support Serbia, Germany declared war on Russia. Two days later, it attacked France and invaded Belgium. Britain immediately declared war on Germany. Europe was at war.