Reason for Entering World War One
One of the long term reasons Russia joined the war was because of their alliance with France and Great Britain, which was known as the Triple Entente. That practically entitled them to fight if violence broke out between any of the Triple Entente countries.
The most immediate reason for Russia joining was that they were committed to protecting Serbia from fighting Austria-Hungary by its self. Then Serbia's Black Hand group assassinated the heir to the Austro-Hungarian kingdom. When Austria declared war on Serbia, Russia declared war on Austria, and in turn Germany declared war on Russia.
One of the long term reasons Russia joined the war was because of their alliance with France and Great Britain, which was known as the Triple Entente. That practically entitled them to fight if violence broke out between any of the Triple Entente countries.
The most immediate reason for Russia joining was that they were committed to protecting Serbia from fighting Austria-Hungary by its self. Then Serbia's Black Hand group assassinated the heir to the Austro-Hungarian kingdom. When Austria declared war on Serbia, Russia declared war on Austria, and in turn Germany declared war on Russia.