Not long after the close of the persecution, Eusebius became bishop of Cæsarea in Palestine, his own home, and held the position until his death. The exact date of his accession cannot be ascertained, indeed we cannot say that it did not take place even before the close of the persecution, but that is hardly probable; in fact, we know of no historian who places it earlier than 313. His immediate predecessor in the episcopate was Agapius, whom he mentions in terms of praise in H. E. VII.32. Some writers have interpolated a bishop Agricolaus between Agapius and Eusebius (see e.g. Tillemont, Hist. Eccles. VII.42), on the ground that his name appears in one of the lists of those present at the Council of Ancyra (c.314), as bishop of Cæsarea in Palestine (see Labbei et Cossartii Conc. I.1475). But, as Hefele shows (Conciliengesch. I.220), this list is of late date and not to be relied upon. On the other hand, as Lightfoot points out, in the Libellus Synodicus (Conc. I.1480), where Agricolaus is said to have been present at the Council of Ancyra, he is called bishop of Cæsarea in Cappadocia; and this statement is confirmed by a Syriac list given in Cowper's Miscellanies, p.41. Though perhaps no great reliance is to be placed upon the correctness of any of these lists, the last two may at any rate be set over against the first, and we may conclude that there exists no ground for assuming that Agapius, who is the last Cæsarean bishop mentioned by Eusebius, was not the latter's immediate predecessor. At what time Agapius died we do not know. That he suffered martyrdom is hardly likely, in view of Eusebius' silence on the subject. It would seem more likely that he outlived the persecution. However that may be, Eusebius was already bishop at the time of the dedication of a new and elegant Church at Tyre under the direction of his friend Paulinus, bishop of that city. Upon this occasion he delivered an address of considerable length, which he has inserted in his Ecclesiastical History, Bk. X. chap.4. He does not name himself as its author, but the way in which he introduces it, and the very fact that he records the whole speech without giving the name of the man who delivered it, make its origin perfectly plain. Moreover, the last sentence of the preceding chapter makes it evident that the speaker was a bishop: "Every one of the rulers (archonton) present delivered panegyric discourses." The date of the dedication of this church is a matter of dispute, though it is commonly put in the year 315. It is plain from Eusebius' speech that it was uttered before Licinius had begun to persecute the Christians, and also, as Görres remarks, at a time when Constantine and Licinius were at least outwardly at peace with each other. In the year 314 the two emperors went to war, and consequently, if the persecution of Licinius began soon after that event, as it is commonly supposed to have done, the address must have been delivered before hostilities opened; that is, at least as early as 314, and this is the year in which Görres places it (Kritische Untersuchungen ueber die licinianische Christenverfolgung, p.8). But if Görres' date (319 a.d.) for the commencement of the persecution be accepted (and though he can hardly be said to have proved it, he has urged some strong grounds in support of it), then the address may have been delivered at almost any time between 315 and 319, for, as Görres himself shows, Licinius and Constantine were outwardly at peace during the greater part of that time (ib. p.14, sq.). There is nothing in the speech itself which prevents this later date, nor is it intrinsically improbable that the great basilica reached completion only in 315 or later. In fact, it must be admitted that Eusebius may have become bishop at any time between about 311 and 318.

The persecution of Licinius, which continued until his defeat by Constantine, in 323, was but local, and seems never to have been very severe. Indeed, it did not bear the character of a bloody persecution, though a few bishops appear to have met their death on one ground or another. Palestine and Egypt seem not to have suffered to any great extent (see Görres, ib. p.32 sq.).