Julian had now succeeded to the Empire, and had entered Constantinople in 361.  He had by this time completely broken with the Church, and renounced even the outward semblance of Christianity.  He persuaded Cæsarius, however, to retain his position at Court, hoping perhaps that he might succeed in perverting him.  This was a matter of deep regret to his father and brother, and they felt, the latter says, obliged to keep the fact from the knowledge of his mother.  Gregory wrote his brother a letter of most affectionate though earnest remonstrance; with the result that Cæsarius soon made up his mind to retire, and put his resolution in practice on the opportunity afforded by the departure of the Emperor from Constantinople to assume the direction of his campaign against the Persians.  Nazianzus was not allowed to remain without attempts being made against its Christianity, for the Prefect of the Province was sent with an armed escort of considerable strength to demand possession of the Church.  But the aged Bishop, supported by his son and by his people, boldly refused to comply with the Imperial commands, and there seemed such a probability of powerful resistance that the Prefect felt compelled to withdraw his force, and never came to Nazianzus again on such an errand.  The Gregorys, father and son, frequently came into collision with Julian during his stay in Cappadocia on his way to Persia; and indeed it is not too much to say that the firm stand which they made on behalf of the right was, under God, the means of diverting the Emperor from his purpose of making a vehement assault upon the faith and rights of the Church in that Province.  As the Abbé Benoît remarks, Julian saw that he must be careful in dealing with a province where Christian faith was such a living power, and where a simple village Bishop could dare to make so stout a stand against Imperial Authority; but he declared his intention of avenging himself upon his opponents on his return from his expedition.  The Providence of God, however, interfered, and he never did return, but was defeated and killed.