History of Christianity

The history of Christianity follows the Christian religion as it developed from its earliest beliefs and practices in the first century, spread geographically in the Roman Empire and beyond, and became a global religion in the twenty-first century.

Christianity originated with the ministry of Jesus, a Jewish teacher and healer who proclaimed the imminent Kingdom of God and was crucified c. AD 30–33 in Jerusalem in the Roman province of Judea. The earliest followers of Jesus were apocalyptic Jewish Christians. Christianity remained a Jewish sect for centuries in some locations, diverging gradually from Judaism over doctrinal, social and historical differences. In spite of occasional persecution in the Roman Empire, the faith spread as a grassroots movement that became established by the third century both in and outside the empire. New Testament texts were written, and church government was loosely organized, in its first centuries, though the biblical canon did not become official until 382.

The Roman Emperor Constantine I became the first Christian emperor in 313. He issued the Edict of Milan expressing tolerance for all religions thereby legalizing Christian worship. He did not make Christianity the state religion, but did provide crucial support. Constantine called the first of seven ecumenical councils needed to resolve disagreements over defining Jesus' divinity. Eastern Christianity was already diverging from Western patterns, language and doctrines by the fourth century. Byzantium was more prosperous than the west, and what became Eastern Orthodoxy was more influential, organized and united with the state than Christianity in the west on into the Middle Ages. During the High Middle Ages, Eastern and Western Christianity had grown far enough apart that differences led to the East–West Schism of 1054. Temporary reunion was not achieved until the year before the fall of Constantinople. Both Islam and crusade negatively impacted Eastern Christianity, and the conquering of Constantinople in 1453 put an end to the institutional church as established under Constantine, though it survived in altered form.

In the Early Middle Ages, missionary activities spread Christianity west and north with monks and nuns playing a prominent role. Combined with politicization, it helped develop East Central Europe, influencing every aspect of medieval life up to and including the 1200s. Various catastrophic circumstances, combined with a growing criticism of the Catholic Church church in the 1300–1500s, led to the Protestant Reformation and its related reform movements. Reform and counter-reformation were followed by the European wars of religion, the return of tolerance as a theological and political option, and the Age of Enlightenment. Christianity also influenced the New World through its connection to colonialism, its part in the American Revolution, the dissolution of slavery in the west, and the long-term impact of Protestant missions.

In the twenty-first century, traditional Christianity has declined in the West, while new forms have developed and expanded throughout the world. Today, there are more than two billion Christians worldwide and Christianity has become the world's largest, and most widespread religion. Within the last century, the center of growth has shifted from West to East and from the North to the Global South.