On June 28, 1914, the heir to the Austrian throne, Archduke Francis Ferdinand, and his wife, Sophia, were assassinated in the Bosnian city of Sarajevo. The assassination was carried out by a Bosnian activist who worked for the Black Hand, a Serbian terrorist organization dedicated to the creation of a pan-Slavic kingdom. Although the Austrian government had no proof the Serbian government had been directly involved in the archduke’s assassination, it saw an opportunity to “render Serbia innocuous once and for all by a display of force,” as the Austrian foreign minister put it. Austrian leaders sought the backing of their German allies, who gave their assurance that Austria-Hungary could rely on Germany’s “full support,” even if “matters went to the length of a war between Austria-Hungary and Russia.” On July 23, Austrian leaders issued an ultimatum to Serbia in which they made such extreme demands that Serbia felt it had little choice but to reject some of them to preserve its sovereignty. Austria then declared war on Serbia on July 28. Still smarting from its humiliation in the Bosnian crisis of 1908, Russia was determined to support Serbia’s cause. On July 28, Tsar Nicholas II ordered a partial mobilization of the Russian army against Austria (see the box on p. 67). The Russian general staff informed the tsar that their mobilization plans were based on a war against both Germany and Austria simultaneously. They could not execute a partial mobilization without creating chaos in the army. Consequently, the Russian government ordered a full mobilization on July 29, knowing that the Germans would consider this an act of war against them. Germany responded by demanding that the Rus- sians halt their mobilization within twelve hours. When the Russians ignored the ultimatum, Germany declared war on Russia on August 1. Under the guidance of General Alfred von Schlieffen, chief of staff from 1891 to 1905, the German general staff had devised a military plan based on the assumption of a two-front war with France and Russia, which had formed a military alliance in 1894. The Schlieffen Plan called for only a minimal troop deployment against Russia. Most of the German army would execute a rapid invasion of France before Russia could become effective in the east or the British could cross the English Channel to help France. To achieve this rapid invasion, the Germans would advance through neutral Belgium, with its level coastal plain, where the army could move faster than on the rougher terrain to the southeast. After the planned quick defeat of the French, the German army would then redeploy to the east against Russia. Under the Schlieffen Plan, Germany could not mobilize its troops solely against Russia; therefore, on August 2, Germany issued an ultimatum to Belgium demanding the right of German troops to pass through Belgian territory and, on August 3, declared war on France. On August 4, Great Britain declared war on Germany, officially in response to this violation of Belgian neutrality but in fact because of Britain’s desire to maintain its world power. As one British diplomat argued, if Germany and Austria were to win the war, “What would be the position of a friendless England?” Thus by August 4, all the great powers of Europe were at war.