Christianity at first was regarded as a sect within Judaism, though it differentiated itself early in the first century CE by breaking with the code of laws that defined Judaism, including the need for circumcision and ritual purity. Early Christianity then grew through the missionary work of the apostles, particularly Paul the Apostle, who traveled throughout the Mediterranean world and beyond the Roman Empire to preach the gospel (good news) of Jesus. (This is often called the Apostolic
Persecution under various Roman emperors only served to strengthen the emerging religion. In the early fourth century, the Emperor Constantine
(c. 272-337) made Christianity the official religion of the Roman
Empire. He also convened the Council of Nicea in 325 CE to quell the religious controversies threatening the Pax Romana ("Roman Peace"), a time of stability and peace throughout the empire in the first and second centuries.
In 1054 the Great Schism, which involved differences over theology and practice, split the church into Eastern Orthodox and Roman Catholic branches. As Islam grew stronger, the Roman Catholic nations of Europe entered a period of Crusades—there were six Crusades in approximately
175 years, from