What happened to Russia during World War 1?

Russia in WWI really pushed WWI further to a more intense battle. As Archduke Ferdinand was assassinated by a Serb student, Russia supported the Serbs (possibly) and in turn, other powers like Austria and Germany entered and supported the opposite side of the confrontation. Which lead to more countries getting involved. Russia was not the country that started WWI but it was a major factor in the war's advancement as a true World War.