From Pope Pius XI’s encyclical Quas Primas (1925):
Since this Holy Year therefore has provided more than one opportunity to enhance the glory of the kingdom of Christ, we deem it in keeping with our Apostolic office to accede to the desire of many of the Cardinals, Bishops, and faithful, made known to Us both individually and collectively, by closing this Holy Year with the insertion into the Sacred Liturgy of a special feast of the Kingship of Our Lord Jesus Christ. This matter is so dear to Our heart, Venerable Brethren, that I would wish to address to you a few words concerning it. It will be for you later to explain in a manner suited to the understanding of the faithful what We are about to say concerning the Kingship of Christ, so that the annual feast which We shall decree may be attended with much fruit and produce beneficial results in the future.
— Quas Primas 6