From Pope Pius XI’s encyclical Quas Primas (1925):
The way has been happily and providentially prepared for the celebration of this feast ever since the end of the last century. It is well known that this cult has been the subject of learned disquisitions in many books published in every part of the world, written in many different languages. The kingship and empire of Christ have been recognized in the pious custom, practiced by many families, of dedicating themselves to the Sacred Heart of Jesus; not only families have performed this act of dedication, but nations, too, and kingdoms. In fact, the whole of the human race was at the instance of Pope Leo XIII, in the Holy Year 1900, consecrated to the Divine Heart. It should be remarked also that much has been done for the recognition of Christ’s authority over society by the frequent Eucharistic Congresses which are held in our age. These give an opportunity to the people of each diocese, district or nation, and to the whole world of coming together to venerate and adore Christ the King hidden under the Sacramental species. Thus by sermons preached at meetings and in churches, by public adoration of the Blessed Sacrament exposed and by solemn processions, men unite in paying homage to Christ, whom God has given them for their King. It is by a divine inspiration that the people of Christ bring forth Jesus from his silent hiding-place in the church, and carry him in triumph through the streets of the city, so that he whom men refused to receive when he came unto his own, may now receive in full his kingly rights.
— Quas Primas 26