Russia felt obligated to protect Serbia due to the fact that a significant number of the Russian population shared a Slavic ethnicity with the Serbian people. Tsar Nicholas II gave the official order to prepare for war on July 30, two days after Austria-Hungary declared war on Serbia. Germany first officially declared war on Russia on August 1, and since Russia was threatened, other European powers were drawn into the war to fulfill their alliances. Therefore it can be argued that because of Russia, the rest of the European powers had to be involved in the conflict, turning it into a world war. So, when asking about the causes of the First World War, it is important to remember that rivalries between European states were intensified by 19th century imperialism. Which led to tension that turned into fear of invasion which in turn led to an intricate system of alliances “made what could have been an isolated crisis in the Balkans become a general war.” While the effects of imperialism may not be the sole cause of the war, they certainly contributed to it