According to the evolution of the Catholic Church in Russia, several events took place that gave birth to Christianity in Russia:
Princess Olga converted to Roman Catholicism. Princess Olga was the first ruler in Rus to convert to Christianity in 945. She was baptized and made several efforts to spread Christianity in Russia.
The pope sent a cardinal and several monks to Kiev. Pope John XV and Sylvester II sent different embassies to Kiev in order to spread Christianity but most of them were killed or died in prison.
Prince Vladimir arranged mass baptisms in Kiev. Princess Olga’s grandson Price Vladimir followed her conversion to Christianity and was baptized. Then he exhorted the people of Kiev to be baptized in the Dnieper River. A mass baptism of the people of Kiev took place and this event marked the beginning of Christianity in Kiev.