1 The supreme Apostolic office which we discharge and the exceedingly difficult condition of these times, daily warn and almost compel Us to watch carefully over the integrity of the Church, the more that the calamities from which she suffers are greater. While, therefore, we endeavour in every way to preserve the rights of the Church and to obviate or repel present or contingent dangers, We constantly seek for help from Heaven - the sole means of effecting anything - that our labours and our care may obtain their wished for object. We deem that there could be no surer and more efficacious means to this end than by religion and piety to obtain the favour of the great Virgin Mary, the Mother of God, the guardian of our peace and the minister to us of heavenly grace, who is placed on the highest summit of power and glory in Heaven, in order that she may bestow the help of her patronage on men who through so many labours and dangers are striving to reach that eternal city. Now that the anniversary, therefore, of manifold and exceedingly great favours obtained by a Christian people through the devotion of the Rosary is at hand, We desire that that same devotion should be offered by the whole Catholic world with the greatest earnestness to the Blessed Virgin, that by her intercession her Divine Son may be appeased and softened in the evils which afflict us. And therefore We determined, Venerable Brethren, to despatch to you these letters in order that, informed of Our designs, your authority and zeal might excite the piety of your people to conform themselves to them.
Source: Supremi Apostolatus Officio (Vatican.va)