She became a member of the Russian Social Democratic Labour Party in 1899 at the age of 27. In 1905, Kollontai was a witness to the popular uprising known as Bloody Sunday at Saint Petersburg in front of the Winter Palace. At the time of the split in the Russian Social Democratic Labour Party between the Mensheviks under Julius Martov and the Bolsheviks under Vladimir Lenin in 1903, Kollontai did not side with either faction at first, and "offered her services to both factions". In 1906, however, disapproving of "the hostile position taken by the Bolsheviks towards the Duma" and despite her being generally a left-winger, she decided to join the Mensheviks.