Why did russia declare war on austria Hungary in 1914?

Russia declared war on Austria-Hungary in 1914 primarily in defense of Serbia, an ally and Slavic nation that was attacked following the assassination of Archduke Franz Ferdinand. Russia viewed itself as the protector of Slavic peoples and sought to support Serbia against Austro-Hungarian aggression. Additionally, the war's outbreak was driven by a complex web of alliances and national interests, with Russia aiming to assert its influence in the Balkans and counter Austro-Hungarian expansion. This declaration was a key event that escalated tensions into World War I.