What historical circumstances led the two Popes to declare the 2 dogmas of Mary with the rare infallible pronouncements?

Most people think that Papal Apostolic Constitutions (which have higher level of authority than most other types of papal documents) are infallible, but in fact only Papal *ex cathedra* statements having 4 characteristics are infallible (see the *Necessary Conditions* section [here](https://fatima.org/news-views/catholic-apologetics-229/)) : 1. Exercising role as the supreme teacher, not simply as private theologian 1. On a matter of faith or morals, not on practical or disciplinary matters 1. Makes an explicit declaration of his intention to define a doctrine Catholics are obligated to assent 1. Makes clear that ALL Catholics, including in all future ages are bound in conscience to this teaching and there have been only [2 instances of this faculty being used](https://uscatholic.org/articles/201105/is-there-a-list-of-infallible-teachings/) , namely for the dogmas of the: 1. Immaculate Conception of Mary (1854, [*Ineffabilis Deus*](https://www.papalencyclicals.net/pius09/p9ineff.htm) by Pope Bl. Pius IX) 1. Assumption of Mary (1950, [*Munificentissimus Deus*](https://www.papalencyclicals.net/pius12/p12munif.htm) by Pope Pius XII) which were defined and taught through an *ex cathedra* [Apostolic Constitution](https://en.wikipedia.org/wiki/Apostolic_constitution) . **Why the two Popes found it expedient to declare the 2 dogmas of Mary using the rare facility of infallible pronouncements (i.e. *ex cathedra*)?** I'm primarily interested in the **historical situations** which must have contributed to the (first?) use of this facility for a Pope to *personally* teach infallibly. Why wouldn't the two Popes use a less authoritative vehicle (such as a *regular* Apostolic Constitution or through a canon of an ecumenical council)? Was there an urgent "heresy" to be dealt with, as it was during the early days of the Protestant Reformation by the Council of Trent? Even if it was urgent, surely a non-*ex cathedra* pronouncement wouldn't be less dogmatic for Catholics? Also, given debate in previous centuries regarding the Immaculate Conception, wouldn't a council be a more appropriate venue for the dogma to be clarified by the whole Church? ----- #### P.S. Impact on ecumenism Now that Vatican II is almost 60 years behind us, the issue of the infallibility of the Pope and these 2 infallible Marian dogmas remained the top reasons why Protestants are hesitant to convert because they would like to see that all that are **necessary** to be believed need to have an *explicit* Biblical basis like every proposition in the Apostle's Creed, for instance. (Just to clarify, *sola scriptura* does NOT say Tradition does NOT have a role, only that Scripture has to NORM Tradition. So as a Protestant who is *not* a Biblicist / proponent of "naked scripture" I can also say that although the 2 dogmas don't have *explicit* support, they are not inherently condemned by Scripture either. For example, even Elijah had his assumption to heaven, and Jesus was immaculately conceived. So I acknowledge that the reasons that most Protestants adduced are largely irrelevant to Catholic way of constructing dogmas, which look to both Scripture and Tradition, with her own hermeneutical principle to interpret Scripture. But STILL, I agree with the Protestant principle that doctrines that do *not* have explicit support should be **optional**, such as baptismal regeneration or the nature of the Eucharist, which Protestants regard as *less* essential than the Trinity, which has become the basis for ecumenism among Protestants.) But history has shown in the past 150 years or so, that both Papal infallibility and Marian dogmas has remained THE single most persistent barrier of entry for **MOST** Protestants to "come back" to the Catholic fold (now *more* than justification by faith alone, for a hint see [2017 Pew Research Survey](https://www.pewresearch.org/religion/2017/08/31/u-s-protestants-are-not-defined-by-reformation-era-controversies-500-years-later/) , 7% and 9% respectively). Because Catholicism elevates them to the status of "**required**" *on the same level of the Trinity*! So it seems **less prudent** (ecumenically) in the age of ecumenism especially since Vatican II that embrace adherents of other religions with its inclusive language regarding the fate of non-Catholic adherents (*cf* *Lumen Gentium*) and designate Protestants as "ecclesial communities" rather than heretics who are anathema, to clarify the 2 Marian teachings as two infallible dogmas using the *ex cathedra* personal pronouncements by the two Popes. To Protestants, it's a **"double whammy"**. Surely both Popes realized this? Why incur the unnecessary ecumenical cost when a non-*ex cathedra* pronouncement PLUS a council document would have sufficed to clarify the matters for Catholics? Yes, the historical **time** is opportune to clarify the Marian dogmas (as Ken Graham pointed out in his answer), but what historical **situation** made it expedient to clarify the dogmas *using* the *ex-cathedra* facility? It's not as though there was an intra-controversy within the Catholic church that risk rupturing the church like the Arian / Donatist controversies, for instance. Or the situation leading to Council of Ephesus declaring that Mary is *theotokos* which Protestants **DO** affirm and consider it as an important support (against heresies) for proper understanding of the Incarnation (see [Gavin Ortlund's arguing for it](https://www.youtube.com/watch?v=vwgHGsODNDw)) . Was it necessary for Catholics to have the matters clarified *ex cathedra*?