From Pope Pius XII’s encyclical Mystici Corporis Christi (1943):
Moreover, We trust that Our exposition of the doctrine of the Mystical Body of Christ will be acceptable and useful to those also who are without the fold of the Church, not only because their good will toward the Church seems to grow from day to day, but also because, while before their eyes nation rises up against nation, kingdom against kingdom, and discord is sown everywhere together with the seeds of envy and hatred, if they turn their gaze to the Church, if they contemplate her divinely-given unity—by which all men of every race are united to Christ in the bond of brotherhood—they will be forced to admire this fellowship in charity, and with the guidance and assistance of divine grace will long to share in the same union and charity.
There is a special reason too, and one most dear to Us, which recalls this doctrine to Our mind and with it a deep sense of joy. During the year that has passed since the twenty-fifth anniversary of Our Episcopal consecration, We have had the great consolation of witnessing something that has made the image of the Mystical Body of Jesus Christ stand out most clearly before the whole world. Though a long and deadly war has pitilessly broken the bond of brotherly union between nations, We have seen Our children in Christ, in whatever part of the world they happened to be, one in will and affection, lift up their hearts to the common Father, who, carrying in his own heart the cares and anxieties of all, is guiding the barque of the Catholic Church in the teeth of a raging tempest. This is a testimony to the wonderful union existing among Christians; but it also proves that, as Our paternal love embraces all peoples, whatever their nationality and race, so Catholics the world over, though their countries may have drawn the sword against each other, look to the Vicar of Jesus Christ as to the loving Father of them all, who, with absolute impartiality and incorruptible judgment, rising above the conflicting gales of human passions, takes upon himself with all his strength the defence of truth, justice and charity.
— Mystici Corporis Christi 5-6