“Since in the course of centuries the holy liturgy has been gaining more and more completeness, it is but natural that this precious mine should come to be further opened in honor of the Virgin Mother. The Order of Saint Francis, it would seem, as well as certain particular churches, such as Rheims and Paris for example— had already taken the initiative, when Urban VI in 1389 instituted today’s solemnity. The Pope counseled a fast on the vigil of the feast, and ordered that it should be followed by an octave; he granted for its celebration the same indulgences as Urban IV had, in the previous century, attached to the festival of Corpus Christi. The Bull of promulgation, stopped by the Pontiff’s death, was again taken up and published by Boniface IX, his successor on the Chair of Peter.
“We learn from the lessons of the office formerly composed for this feast, that the object of its institution was, as Urban conceived it, to obtain the cessation of the schism then desolating the Church. The Papacy, exiled from Rome for 70 years, had barely re-entered it, when hell, infuriated at a return which crossed all its plans, had taken revenge by ranging under two leaders the flock of the one sheepfold. So deep was the obscurity wherewith miserable intrigues contrived to cover the authority of the legitimate shepherd, that numbers of churches, in all good faith, began to hesitate, and ended at last in preferring the deceptive staff of a hireling. Thicker yet was the darkness to grow, till night should be so dense, that for a moment the conflicting mandates of three Popes would simultaneously spread through the world; whilst the faithful, struck with stupor, would be at an utter loss to discern accurately which was the voice of Christ’s true Vicar. Never had the bride of the Son of God been in a more piteous situation. But Our Lady, to whom the true Pontiff had turned at the first rising of the storm, did not betray the Church‘s confidence. During all those years while the unfathomable justice of the Most High let the powers of hell hold sway, she stood for the defense of holy Church, trampling the head of the old serpent so thoroughly under her victorious foot, that in spite of the terrific confusion he had stirred up, he was unable to sully the faith of the people. Their attachment was steadfast to the unity of the Roman See, whosoever might be, in this uncertainty, its veritable occupant. Thus the West, divided in fact, but in principle ever one and undivided, reunited herself spontaneously as soon as God‘s moment came for the return of light….
“It was now to be shown that such a return of nations, in the very midst even of the tempest, was indeed the work of her who had been called upon by the pilot, half a century before, to succor the bark of Peter. Even they of the fractious assembly of Basle gave proof of this, in a way which has unfortunately been too much overlooked by historians who undervalue the high importance that liturgical facts hold in the history of Christendom. When about to separate, these last abettors of the schism devoted the 43rd session of their pretended council to the promulgation of this feast of the Visitation, in the establishment of which Urban VI had, from the outset, placed all his hopes. Notwithstanding the resistance of some of the more obstinate, the schism may, from that hour, be said to have ended. The storm was subsiding; the name of Mary, invoked thus by both sides, shone resplendent as the sign of peace amidst the clouds, even as the rainbow in its sweet radiance unites both extremities of the horizon. ‘Look upon it,’ says the Holy Ghost, ‘and bless Him that made it: it is very beautiful in its brightness. It encompasseth the heaven about with the circle of its glory: the hands of the Most High have displayed it.’”
— from the Liturgical Year