Why did the czar order full mobilization of the Russian army on July 29 1914?

Czar Nicholas II ordered full mobilization of the Russian army on July 29, 1914, in response to the escalating tensions following the assassination of Archduke Franz Ferdinand of Austria. Russia aimed to support its Slavic ally, Serbia, which was facing aggression from Austria-Hungary. The mobilization was seen as a necessary step to demonstrate Russia's commitment to defending Serbia and to deter further military action by Austria-Hungary, but it ultimately contributed to the outbreak of World War I. This decision also reflected the broader entanglements of alliances and nationalistic fervor in Europe at the time.