There are two pervasive myths about S Pius V's liturgical interventions which will doubtless go on being purveyed until the Eschaton.
(1) That he suppressed the local rites of the Middle Ages, only permitting the survival of those which had existed for more than 200 years. He was a centraliser and a standardiser.
(2) That his actions, following on from Trent, are closely analogous to, and provide a close precedent for, what Paul VI did after Vatican II.
Each of these myths is a travesty of history. Each results from a reading of History with the hindsight of knowing What Happened Afterwards, instead of trying to understand events in their own historical contexts. Since devils reside in details, and since I have written before about what he did with his Missal, I shall focus today on what he did to the Breviary.
The papal document Quod a nobis, which introduces the 'Tridentine Breviary', repays careful reading. The Divine Office put in place by Gelasius and Gregory and reformed by Gregory VII had, S Pius tells us, diverged ab antiqua constitutione. So the pope wishes it to be recalled ad pristinam orandi regulam. Some people had deformed this praeclara constitutio by mutilations and changes; an awful lot of people (plurimi) had been seduced (allecti) by the brevity of a Breviary produced by the Spanish Cardinal Quignon. Even worse, in provincias paulatim irrepserat prava illa consuetudo ["that depraved custom"], namely, that bishops in churches which, from the beginning, had used the Roman Office, were producing privatum sibi quisquam Breviarium.
What S Pius V is dealing with here is the chaotic liturgical result of a century of printing. It may be difficult for us to appropriate imaginatively the differences that this invention made. Only in the age of this new technology could trendy clergy buy and use in vast numbers the new slick and fast Quignon Breviary; only now could meddling bishops, full of Good Ideas, thrust their latest clever novelties with ease upon their helpless dioceses. The words of S Pius seem almost to describe the chaos which was to follow under Pius XII and his successors: "Hence the total disruption of divine worship in so many places; hence a complete ignorance among the clergy of ecclesiastical rites and ceremonies; so that numberless ministers of the churches carry out their duty unbecomingly, not without enormous offence to the devout".
S Pius was reacting to to this technology-driven chaos by a reinstatement of Tradition; by the elimination of novelty and by a return to what had been received. Hence, he provided a form of the Roman Breviary carefully emended by the best scholarship available to him. It was, of course, a paradox that his reform was itself carried through by the use of the same technology which had created the problem!! But that paradox does nothing to change the fact that his action was an assertion of Tradition, a repression of innovation.
S Pius V's reform was thus an act of deliberate and profound conservatism. This is shown by his treatment of local usages which dated from well before the invention of printing. As for uses which were of more than two centuries standing: "that ancient right of saying and singing their office, we do not take away". Recognising, however, that many who possessed such ancient usages might nevertheless themselves prefer the revision which he is now promulgating, he permits them to adopt it, but only if the Bishop and the entire chapter agree. Entire!! Come-lately diocesans were thereby restrained, according to the words of this legislation, from abolishing the ancient uses of their churches; apparently, it needed only one curmudgeonly traditionalist on the Chapter to interpose his veto and thus to preserve the local customs. This seems to me a fairly rigorous affirmation of the the traditional diversities with which a process of organically evolving liturgy had endowed local churches, combined with a determination to eliminate novel fancies which had corrupted liturgy since printing made it easy for hierarchs to impose their whimsies. I wonder what he might have said could he have known that, four hundred years later, his own successors would be using printing to impose their whimsies!
S Pius V's reforms, as I have said, are commonly described as symptoms of counter-reformation centralisation and as an attempt rigorously to standardise the worship of the Latin Church. I think this profoundly and anachronistically misreads both the liturgical situation which he is addressing; and the legal framework which he carefully puts in place. Previous popes had fairly recently flirted with the idea of radical revisions of the Breviary, intending thus to bring it into line with the ('Humanist') fashions of their age. But in S Pius V, a truly great pontiff, we see at its very best the ancient function of the Roman Church as a remora against innovation; as well as an assertion of the principle that the Tradition is not ours to destroy, but to hand on carefully with - as Vatican II actually says - only such changes as grow organically out of what is already there, and are truly necessary. (Among later pontiffs, perhaps Benedict XIV came closest to the instincts of S Pius V.)
If S Pius V had been a B Paul VI, he would have confirmed and extended the papal permission for the use of the Quignon breviary; he would have encouraged diocesan bishops to forge ahead with their own 'inculturations'. He did nothing of the sort; he did the opposite. Perhaps the only faint resemblance to the events of the 1960s is S Pius's somewhat root-and-branch approach to a Calendar which had become overloaded (calendars constantly silt up and then need to be dredged; it's a natural cycle like the successions of ice ages and interglacials)*. But that had the result of revealing old Roman treasures which an excessive Sanctorale had left unchanged in the physical texts while the newer insertions had been preventing their actual use. In the 1950s and 1960s, it was those archaic features themselves that fell victim to an elite in a hurry (during this Advent season, we might particularly remember the demise of the old Excita Sunday collects).
You are entitled to think what you like about the events of the 1960s. I have no power to pop you into my own personal private prison! But please do not go around saying that what B Paul VI did after Vatican II was indistinguishable from S Pius V had done after Trent.
It. Was. Nothing. Of. The. Sort!!
*The elimination as 'non-Biblical' of S Anne and the Presentation of our Lady was very swiftly reversed by a succeeding pontiff.
Attempts to assert a parallel between S Pius V and Paul VI also involve a massive suggestio falsi: that S Pius's 'revision' was as radical, and with as little rootedness in what had gone before, as B Paul's.