Socrates Scholasticus concludes his lengthy description of the divisions that abounded in the early church, from the 22nd chapter of his Ecclesiastical History (NPNF II.2):
Let us now return to the subject we were previously treating of, the fact that the Church once divided did not stay with that division, but that those separated were again divided among themselves, taking occasion from the most trivial grounds.
Socrates Scholasticus, “Ecclesiastical History,Book V, Chapter 23”, in Nicene and Post-Nicene Fathers, Series II, Vol. 2 (pgs. 131-134).
The many fractures and splits he details in the paragraphs before this summation were clearly caused by Martin Luther and the Protestant Reformation, which is why all good Christians should submit to the Pope. How Luther pulled this off so many years before his birth we must credit to the wiles of Satan.