Final answer:
Germany declared war on Russia following Czar Nicholas' mobilization of troops towards the German-Austrian border, which contributed to the outbreak of World War I.
Step-by-step explanation:
The result of Czar Nicholas' mobilization of his troops towards the German-Austrian border was that Germany declared war on Russia. This mobilization was in response to Austria-Hungary's declaration of war on Serbia, which occurred after Serbia did not meet the demands of the Austrian ultimatum following the assassination of Archduke Franz Ferdinand. Germany, allied with Austria-Hungary and having assured them of its support, found itself inevitably joining the conflict. This set of actions contributed to the complex web of alliances and conflicts that sparked World War I.