The IWD was considered an important event in Russia, respectively the Soviet Union, and designated as a national holiday (and still is).
It was first celebrated 1913 on the eve of the First World War when Women and Men protested for peace and better working conditions. With the end of the war, millions of Russian soldiers dead, Russian Women in 1917 chose to strike for “bread and peace”. This strike started on February 23 on the Julian calendar (March 8 in the Gregorian calendar) and within the next couple of days more and more women and men joined in. The Czar was forced to abdicate and the provisional government granted women the right to vote.
Due to these events as well as discussion beforehand the IWD was moved to March 8th and has been celebrated on these days since 1918.