Christianity in the 4th century

Christianity in the 4th century was dominated in its early stage by Constantine the Great and the First Council of Nicaea of 325, which was the beginning of the period of the First seven Ecumenical Councils (325–787), and in its late stage by the Edict of Thessalonica of 380, which made Nicene Christianity the state church of the Roman Empire.

With Christianity the dominant faith in some urban centers, Christians accounted for approximately 10% of the Roman population by 300, according to some estimates. Roman Emperor Diocletian launched the bloodiest campaign against Christians that the empire had witnessed. The persecution ended in 311 with the death of Diocletian. The persecution ultimately had not turned the tide on the growth of the religion. Christians had already organized to the point of establishing hierarchies of bishops. In 301 the Kingdom of Armenia became the first nation to adopt Christianity. The Romans followed suit in 380.

In April 311, Galerius, who had previously been one of the leading figures in the persecutions, issued an edict pg the practice of the Christian religion under his rule. From 313 to 380, Christianity enjoyed the status of being a legal religion within the Roman Empire. It had not become the sole authorized state religion, however it gradually gained prominence and stature within Roman society. After halting the persecutions of the Christians, Galerius reigned for another 2 years. He was then succeeded by an emperor with distinctively pro Christian leanings, Constantine the Great.

Christian sources record that Constantine experienced a dramatic event in 312 at the Battle of Milvian Bridge, after which Constantine claimed the emperorship in the West. According to these sources, Constantine looked up to the sun before the battle and saw a cross of light above it, and with it the Greek words "ΕΝ ΤΟΥΤΩ ΝΙΚΑ" ("by this, conquer!", often rendered in the Latin "in hoc signo vinces"); Constantine commanded his troops to adorn their shields with a Christian symbol (the Chi-Ro), and thereafter they were victorious. How much Christianity Constantine adopted at this point is difficult to discern; most influential people in the empire, especially high military officials, were still pagan, and Constantine's rule exhibited at least a willingness to appease these factions.

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