Rome could come to terms with the God of Hosts." When Constantine became emperor of the Western Roman Empire in 312, he attributed his victory to the Christian God.Many soldiers in his army were Christians, and his army was his base of power.With Licinius, (Eastern Roman emperor), he issued the Edict of Milan which mandated toleration of all religions in the empire.
The New Testament records Jesus' activities and teaching, his appointment of the twelve Apostles, and his instructions to them to continue his work.
Catholics hold that Saint Peter was Rome's first bishop and the consecrator of Linus as its next bishop, thus starting the unbroken line which includes the current pontiff, Pope Francis.
In 313, the struggles of the Early Church were lessened by the legalisation of Christianity by the Emperor Constantine I.
In 380, under Emperor Theodosius I, Catholicism became the state religion of the Roman Empire by the decree of the Emperor, which would persist until the fall of the Western Empire, and later, with the Eastern Roman Empire, until the Fall of Constantinople.
The Second Vatican Council in the 1960s introduced the most significant changes to Catholic practices since the Council of Trent four centuries before.