Did the Reformation split the Church?

i) As well all know, the Church was unified until the Protestant Reformers splintered it. Just ask any Catholic apologist. 

But what about the pre-Reformation church? 

In the full and primitive sense of the word every serious rupture of unity and consequently every heresy is a schism. This article, however, will pass over the long series of heresies and treat only those defections or religious sects to which historians commonly give the specific name of schisms, because most frequently, and at least in the beginning of each such sectarian division, doctrinal error was only an accessory. They are treated in chronological order and the most important only briefly, these being the subjects of special articles in the ENCYCLOPEDIA.

(1) Mention has already been made of the "schisms" of the nascent Church of Corinth, when it was said among its members: "I indeed am of Paul; and I am of Apollo; and I of Cephas; and I of Christ." To them St. Paul's energetic intervention put an end.

(2) According to Hegesippus, the most advanced section of the Judaizers or Ebionites at Jerusalem followed the bishop Thebutis as against St. Simeon, and after the death of St. James, A.D. 63, separated from the Church.

(3) There were numerous local schisms in the third and fourth centuries. At Rome Pope Callistus (217-22) was opposed by a party who took exception to the mildness with which he applied the penitential discipline. Hippolytus placed himself as bishop at the head of these malcontents and the schism was prolonged under the two successors of Callistus, Urban I (222-30) and Pontianus (230-35). There is no doubt that Hippolytus himself returned to the pale of the Church (cf. d'Alès, "La théol. de s. Hippolyte", Paris, 1906, introduction).

(4) In 251 when Cornelius was elected to the See of Rome a minority set up Novatian as an antipope, the pretext again being the pardon which Cornelius promised to those who after apostatizing should repent. Through a spirit of contradiction Novatian went so far as to refuse forgiveness even to the dying and the severity was extended to other categories of grave sins. The Novatians sought to form a Church of saints. In the East they called themselves katharoi, pure. Largely under the influence of this idea they administered a second baptism to those who deserted Catholicism to join their ranks. The sect developed greatly in the Eastern countries, where it subsisted until about the seventh century, being recruited not only by the defection of Catholics, but also by the accession of Montanists.

(5) During the same period the Church of Carthage was also a prey to intestinal divisions. St. Cypnan upheld in reasonable measure the traditional principles regarding penance and did not accord to the letters of confessors called libelli pacis the importance desired by some. One of the principal adversaries was the priest Donatus Fortunatus became the bishop of the party, but the schism, which was of short duration took the name of the deacon Felicissimus who played an important part in it.

(6) With the dawn of the fourth century Egypt was the scene of the schism of Meletius, Bishop of Lycopolis, in the Thebaid. Its causes are not known with certainty; some ancient authors ascribe it to rigorist tendencies regarding penance while others say it was occasioned by usurpation of power on the part of Meletius, notably the conferring of ordinations outside his diocese. The Council of Nicæa dealt with this schism, but did not succeed in completely eradicating it; there were still vestiges of it in the fifth century.

(7) Somewhat later the schism of Antioch, originating in the troubles due to Arianism, presents peculiar complications. When the bishop Eustathius, was deposed in 330 a small section of his flock remained faithful to him, but the majority followed the Arians. The first bishop created by them was succeeded (361) by Meletius of Sebaste in Armenia, who by force of circumstances became the leader of a second orthodox party. In fact Meletius did not fundamentally depart from the Faith of Nicæa, and he was soon rejected by the Arians: on the other hand he was not recognized by the Eustathians, who saw in him the choice of the heretics and also took him to task for some merely terminological differences. The schism lasted until about 415. Paulinus (d. 388) and Evagrius (d. 392), Eustathian bishops, were recognized in the West as the true pastors, while in the East the Meletian bishops were regarded as legitimate.

(8) After the banishment of Pope Liberius in 355, the deacon Felix was chosen to replace him and he had adherents even after the return of the legitimate pope. The schism, quenched for a time by the death of Felix, was revived at the death of Libenius and the rivalry brought about bloody encounters. It was several years after the victory of Damasus before peace was completely restored.

(9) The same period witnessed the schism of the Luciferians. Lucifer, Bishop of Calaris, or Cagliari, was displeased with Athanasius and his friends who at the Synod of Alexandria (362) had pardoned the repentant Semi-Arians. He himself had been blamed by Eusebius of Vercelli because of his haste in ordaining Paulinus, Bishop of the Eustathians, at Antioch. For these two reasons he separated from the communion of the Catholic bishops. For some time the schism won adherents in Sardinia, where it had originated, and in Spain, where Gregory, Bishop of Elvira, was its chief abettor.

(10) But the most important of the fourth-century schisms was that of the Donatists. These sectaries were as noted for their obstinacy and fanaticism as for the efforts and the writings rather uselessly multiplied against them by St. Augustine and St. Optatus of Milevis.

(11) The schism of Acacius belongs to the end of the fifth century. It is connected with the promulgation by the emperor Zeno of the edict known as the Henoticon. Issued with the intention of putting an end to the Christological disputes, this document did not satisfy either Catholics or Monophysites. Pope Felix II excommunicated its two real authors, Peter Mongus, Bishop of Alexandria, and Acacius of Constantinople. A break between the East and the West followed which lasted thirty-five years. At the instance of the general Vitalian, protector of the orthodox, Zeno's successor Anastasius promised satisfaction to the adherents of the Council of Chalcedon and the convocation of a general council, but he showed so little good will in the matter that union was only restored by Justin I in 519. The reconciliation received official sanction in a profession of Faith to which the Greek bishops subscribed, and which, as it was sent by Pope Hormisdas, is known in history as the Formula of Hormisdas.

(12) In the sixth century the schism of Aquilea was caused by the consent of Pope Vigilius to the condemnation of the Three Chapters (553). The ecclesiastical provinces of Milan and Aquilea refused to accept this condemnation as valid and separated for a time from the Apostolic See. The Lombard invasion of Italy (568) favoured the resistance, but from 570 the Milanese returned by degrees to the communion of Rome; the portion of Aquilea subject to the Byzantines returned in 607, after which date the schism had but a few churches. It died out completely under Sergius I, about the end of the eighth century.

(13) The ninth century brought the schism of Photius, which, though it was transitory, prepared the way by nourishing a spirit of defiance towards Rome for the final defection of Constantinople.

(14) This took place less than two centuries later under Michael Cerularius who at one stroke (1053) closed all the churches of the Latins at Constantinople and confiscated their convents. The deplorable Greek schism (see GREEK CHURCH), which still subsists, and is itself divided into several communions, was thus consummated. The two agreements of reunion concluded at the Second Council of Lyons in 1274, and at that of Florence in 1439, unfortunately had no lasting results; they could not have had them, because on the part of the Greeks at least they were inspired by interested motives.

(15) The schism of Anacletus in the twelfth century, like that of Felix V in the fifteenth, was due to the existence of an antipope side by side with the legitimate pontiff. At the death of Honorius II (1130) Innocent II had been regularly elected, but a numerous and powerful faction set up in opposition to him Cardinal Peter of the Pierleoni family. Innocent was compelled to flee, leaving Rome in the hands of his adversaries. He found refuge in France. St. Bernard ardently defended his cause as did also St. Norbert. Within a year nearly all Europe had declared in his favour, only Scotland, Southern Italy, and Sicily constituting the other party. The emperor Lothaire brought Innocent II back to Rome, but, supported by Roger of Sicily the antipope retained possession of the Leonine City, where he died in 1138. His successor Victor IV two months after his election, sought and obtained pardon and reconciliation from the legitimate pontiff. The case of Felix V was more simple. Felix V was the name taken by Amadeus of Savoy, elected by the Council of Basle, when it went into open revolt against Eugenius IV, refused to disband and thus incurred excommunication (1439). The antipope was not accepted save in Savoy and Switzerland. He lasted for a short time with the pseudo-council which had created him. Both submitted in 1449 to Nicholas V, who had succeeded Eugenius IV.

(16) The Great Schism of the West is the subject of a special article (WESTERN SCHISM); see also COUNCIL OF CONSTANCE; COUNCIL OF PISA.

http://www.newadvent.org/cathen/13529a.htm

I'm deliberately quoting from a partisan source. Not just a Catholic source, but the pre-Vatican II edition, which is very polemical. So by Catholic standards, by their own admission, church history has always been marked by severe divisions. This is their own biased version of events. 

ii) In addition, what the Protestant Reformed exposed was the artificiality of the prior unity. The papacy forcibly superimposed a veneer of unity, but once the heavy hand of the papacy lost its steely grip, "the Church" split into many factions. Superficial conformity had camouflaged the underlying lack of agreement. That's what happens when force takes the place of persuasion and conviction.