Complex sentence: Soon after their conversion to Christianity, the people of Russia began performing pilgrimages to the Holy Land, and by the 19th century the annual number of pilgrims reached into the thousands, flocking annually to the Holy Land, mainly on Easter.
Split into simpler sentences: Soon after their conversion to Christianity, the people of Russia began performing pilgrimages to the Holy Land. By the 19th century, thousands of pilgrims flocked annually to the Holy Land, mainly on Easter.