 Later, they expanded to the north of the Mediterranean Sea to include Western, Central, and Southeastern Europe.Christianization of Ireland (5th century), Christianization of Bulgaria (9th century), Christianization of Kievan Rus' (Russia, Ukraine, Belarus; 10th century), Christianization of Scandinavia (Denmark, Norway, Sweden; 12th century) and Christianization of Lithuania (14th century) brought the rest of present-day European territory into Western civilization.Historians, such as Carroll Quigley in ""The Evolution of Civilizations"", contend that Western civilization was born around AD 500, after the total collapse of the Western Roman Empire, leaving a vacuum for new ideas to flourish that were impossible in Classical societies.