 Russia's industrial base and railway network had significantly improved since 1905, although from a relatively low base; in 1913, Tsar Nicholas approved an increase in the Russian Army of over 500,000 men.Although there was no formal alliance between Russia and Serbia, their close bilateral links provided Russia with a route into the crumbling Ottoman Empire, where Germany also had significant interests.Combined with the increase in Russian military strength, both Austria and Germany felt threatened by Serbian expansion; when Austria invaded Serbia on 28 July 1914, Russian Foreign Minister Sergei Sazonov viewed it as an Austro-German conspiracy to end Russian influence in the Balkans.