Positive: The eastern and western Roman Empires had gradually drifted apart due to differences in language (the Eastern Empire spoke Greek, the western Latin), religion (Orthodox vs. Roman Catholic Christianity) and geography. The Crusades marked an end the isolation of the two empires and a gradual recovery of Greek learning in the west (especially as eastern scholars fled to fall of Constantinople and moved to Italy), leading, in part to the Renaissance.

Negative: The western intervention in the wars in the east led to increasing tensions between Christendom and Islam, which still influence politics in the 21st century.