Cardinal Pie of Poitiers (1815-1880), one of the great champions of the Kingship of Christ during the 19th Century, again and again urged Catholics never to relinquish the struggle for God’s rights, never to become resigned to the dethronement of Christ the King.
Speaking of the Church’s mission to the nations of the world, the Cardinal said: “Remark the last words addressed by Our Lord to His Apostles before He ascended into Heaven: ‘All power is given to Me in Heaven and on earth. Going therefore, teach ye all nations.’ Notice that Our Lord Jesus Christ does not say all men, all individuals, all families, but all Nations. He does not merely say: Baptize children, teach the catechism, bless marriages, administer the sacraments, give religious burial to the dead. Of course, the mission He confers on the Apostles comprises all that, but it comprises more than that, for it has a public and social character. Jesus Christ is King of peoples and Nations.” 
Again, when commenting on the first three petitions of the Our Father, “Hallowed be Thy name, Thy Kingdom come, Thy Will be done on earth as it is in Heaven,” he insisted that all these demand the public social reign of God, through the acknowledgment of Our Lord Jesus Christ, Whom the Father has sent. The Name of God is not hallowed as It should be, if It is not hallowed publicly and socially. Our Lord’s Kingdom is meant to come, not only in individual souls and in Heaven, but on earth, through the submission of States and Nations to His rule. The will of God is not done on earth as it is in Heaven, if organized societies here below do not acknowledge their duties to God through Our Lord Jesus Christ. “The Catholic,” he goes on to say, “is not a being who shuts himself up in an oratory, from which the tumult of the world is carefully excluded and who, occupied exclusively with saving his own soul, takes no interest in the way the world is going ... When Our Lord taught His Apostles the Our Father, He made it clear that none of His followers could accomplish the first act of religion, which is prayer, without putting himself in relation with all that can advance or retard, favor or hinder, the reign of God on earth, and he must do this in proportion to his intellectual attainments and to the extent of the horizon open before him ... As long as this world lasts, let us never consent to limit the reign of God to Heaven or even to Heaven and the interior of souls. ‘Thy Will be done on earth as it is in Heaven.’ The dethronement of God on earth is a crime, to which we must never become resigned. Let us never cease to protest against it.” 
This is especially necessary nowadays when proposals are being made in view of remedying economic and financial evils, while leaving God’s Rights and Our Lord’s Program for their orderly acknowledgment out of account. “There would be today neither Socialism nor Communism,” wrote Pope Pius XI, “if the rulers of the Nations had not scorned the teachings and maternal warnings of the Church. On the basis of Liberalism and Laicism, they wished to build other social edifices which, powerful and imposing as they seemed at first, all too soon revealed the weakness of their foundations, and today are crumbling one after another before our very eyes, as everything must crumble that is not grounded on the one cornerstone which is Christ Jesus.” 
 The Kingship of Christ according to Cardinal Pie of Poitiers, pp. 24, 25.
 The Kingship of Christ according to Cardinal Pie of Poitiers, pp. 26, 92.
 Encyclical Letter, Divini Redemptoris, On Atheistic Communism.
Taken from The Kingship of Christ and Organized Naturalism