6 Moved by these thoughts and by the examples of Our Predecessors, We have deemed it most opportune for similar reasons to institute solemn prayers and to endeavour by adopting those addressed to the Blessed Virgin in the recital of the Rosary to obtain from her son Jesus Christ a similar aid against present dangers. You have before your eyes, Venerable Brethren, the trials to which the Church is daily exposed; Christian piety, public morality, nay, even faith itself, the supreme good and beginning of all the other virtues, all are daily menaced with the greatest perils.
Source: Supremi Apostolatus Officio (Vatican.va)