History of Christianity

The history of Christianity began with the life of Jesus, an itinerant Jewish preacher and teacher, who was crucified in Jerusalem c. AD 30–33. His followers proclaimed that he was the incarnation of God, and had risen from the dead. In the two millennia since, Christianity has spread across the world, becoming the world's largest religion with over two billion adherents worldwide.

Christianity was initially a grassroots movement spread by apostles, in cities, reaching critical mass by the third century when it grew to over a million adherents. The support of the Roman emperor Constantine in the early 300s was important in transforming it into an organized religion with a formalized religious text. Art, architecture, and literature blossomed. Competing theological doctrines led to divisions, the response of the Nicene Creed of 325, which led to the 5th-century Nestorian schism and created the Church of the East and Oriental Orthodoxy. While the Western Roman Empire ended in 476, its successor states and its eastern compatriot—which became the Byzantine Empire—remained Christian.

In the Middle Ages, western monks preserved culture and provided social services. The Arab conquests devastated many Christian communities in the Middle East and North Africa, but Christianization continued in Europe and Asia and helped form the states of Eastern Europe. The 1054 East–West Schism saw the Byzantine Empire's Eastern Orthodoxy and the Catholic Church of the West separate. In spite of differences, the East requested western aid against the Turks resulting in the Crusades. Faced with internal and external challenges, the church fought heresy and established courts of inquisition. Gregorian reform led to a more centralized and bureaucratic Catholicism. Artistic and intellectual advances among western monks laid the foundations for the Renaissance and the scientific revolution.

The Western Schism and various European crises in the 14th century led to intense criticism of the Church and the 16th-century Reformation, out of which arose Protestantism. Quarrelling royal houses precipitated the European wars of religion. Different parts of Christianity variously influenced European colonialism, the Age of Enlightenment, the American and French Revolutions, the Industrial Revolution, and the Atlantic slave trade. Some Protestants created biblical criticism while others responded to rationalism with Pietism and religious revivals that created new denominations. Protestants advocated for religious tolerance, the separation of church and state and moral reform while nineteenth century missionaries laid the linguistic and cultural foundation for many nations. In the 20th century, Christianity declined in parts of the West but grew vastly in the East and the Global South.