Which of these events happened last? .
germany declared war against russia..
russia mobilized its army to support serbia..
france refused germany’s request to remain neutral..
austria-hungary sought germany’s support against serbia..

The event that happened last was that France refused Germany’s request to remain neutral. On July 28, 1914, Autria- Hungary declares war against Serbia, with Germany’s support. On July 30, Russia mobilizes its army to support Serbia. On August 1, after giving it an ultimatum, Germany declares war against Russia and gives another ultimatum to France. Germany requests France to remain neutral in the Russian conflict. To guarantee its neutrality, France must deliver the Verdun and Toul fortresses. France refuses Germany's request alleging that it will act according to its own interests. Consequently, on August 3, 1914, Germany declares war against France.