This question cannot, in my judgement, be adaquately answered in the absence of an analysis of the underlying causes of the War.

Explanations of the underlying cause of the War tend to be contentious, frequently confusing, and dependent on the bias of the historian telling the story. I'm what is known as a Realist in terms of international relations theory, which means that I see power as the key variable in understanding the relationships between sovereign states.

Realism is a pretty simple theory, and the eminent theorist of International Relations John Mearsheimer of the University of Chicago wrote an article which you can read called ("Anarchy and the Struggle for Power") [http://www.ucs.mun.ca/~russellw/Teaching_files/Mearsheimer%20-%20Realism.pdf] if you'd like to understand the assumptions we make when we analyze topics like this one.

The underlying cause of the conflict was the absence of a clear balance of power in Europe. Austria and Russia came into conflict because there was no clear balance of power between them and because of their geographic proximity to each other. The Austro-Hungarian empire extended from central Europe into the Balkans, and Russia's empire likewise extended from the far reaches of Asia all the way into Eastern Europe. Both states were Great Powers with considerable offensive military capabilities. Both wanted to dominate the Balkans in order to ensure their security vis-a-vis one another. In 1908, Austria annexed Bosnia & Herzegovina, which made the Russians fearful that they Austrians were extending their influence to the East, right up towards Russia's doorstep. Russia attempted to destabilize Austria in the Balkans internally by advocating an ideology called Pan-Slavism, a form of ethnic nationalism which asserted that Slavs shouldn't be ruled by Germanic non-Slaves like the Austrians. Russia also used the independent state of Serbia as a client state in the Balkans in order to balance against Austrian influence elsewhere in the region. Austria hitched its wagon to the rising power of Germany, who were likewise fearful of the Russians and who shared a border with Russia. Serbia itself was an issue of minor importance, and the real issue was the roughly equitable distribution of power between the Triple Alliance and the Entente. Russia mobilized against Austria when Austria declared war on Serbia because Russia wanted to eliminate the Austrian and German threats to her west and thereby ensure her own security against foreign domination.