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Christianity, as a religion, originated from the teachings of Jesus, a son of a carpenter. The timeline of the expansion of Christianity throughout the world  started in the 1st century AD, after the death of Jesus. This religion was spread by Jesus’ disciples, emperors, nuns, and monks around the Mediterranean region and later throughout the world. Today, there are more than two billion Christians in the world.

Explanation:

The core of the religion is based on the life, the death, and  the resurrection of Jesus Christ, or Messiah. It was only after the death and the resurrection of Jesus from Nazareth that Christianity was formed into religious teaching. Those who followed the Prophet during his life believed that he resurrected on the third day after his death and was indeed the Messiah.

Following their teacher, the disciples of Christ preached love toward God, the Creator, the importance of forgiveness, and repentance of sins. Early Christianity was distributed in the Roman Empire in the first centuries AD. The reason why Christianity managed to succeed in the Roman Empire is the active work of missionaries who preached the gospel of Jesus Christ.

One of the first missionaries was apostle Paul, who claimed his encounter with the Messiah after his resurrection. Paul worked to establish numerous churches throughout the Roman Empire and outside of it. Also, he was the author of thirteen books of the New Testament of the Bible, which is the basic holy text of Christianity.

There were many other important people who followed the example of Paul and made their contribution to the expansion of Christianity around the world. However, the work of apostle Paul is regarded as a significant achievement without which Christianity would not have reached such a scale of influence.

There were significant difficulties in preaching the word of Christ in the Roman Empire because of the continuous persecutions of Christians. Since more and more citizens of the empire refused to worship the emperor and converted to Christianity instead, the authorities tried to eliminate the spreading religion by all means, sometimes even death. However, the apostles and their followers were numerous and withstood the historical difficulties.

After the deaths of apostles who designated the general directions of the religion, bishops continued their work and spread the Christian religion in the countries neighboring with Rome. Thus, Christianity was present all over the Mediterranean territory but in slightly differing interpretations of the scriptures.

Importantly, the crucial point in the history of Christian expansion was the conversion to Christianity of the Roman Emperor, Constantine. He defined Christianity as the righteous religion of Rome and tried to unify different streams of Christianity. Nonetheless, by the time of the collapse of the Roman Empire, religion emerged in several branches, which are now known as Orthodox, Catholic, and Protestant churches.

In the middle ages, Christianity expanded over European countries and became a leading religious doctrine there. In the later stages of the history of the religion, many factors contributed to the spread of the doctrine. For example, the exploration of new lands by Europeans enabled an expansion of Christianity to the Americas. As of today, there are almost two billion Christians in the world, which makes this religion one of the leading doctrines in the world that has a reach history of its development.