On 1st November, 1914, Pope Benedict XV wrote his Encyclical Letter Ad Beatissimi Apostolorum to the Patriarchs, Primates, Archbishops, Bishops, and Other Local Ordinaries in Peace and Communion with the Apostolic See appealing for Peace:
"27. Now, in order that all these recommendations should have the results We hope for, you know, Venerable Brethren, how necessary is the prudent and assiduous work of those whom Christ our Lord sends as "labourers into His harvest," that is to say the clergy. Remember, therefore, that your chief care must be to foster in the holiness which becomes them the clergy you already possess, and worthily to form your ecclesiastical students for so sacred an office by the very best available education and training. And although your carefulness in this respect calls for no stimulus, nevertheless We exhort and even implore you to give the matter your most careful attention. Nothing can be of greater importance for the good of the Church; but as Our Predecessors of happy memory, Leo XIII and Pius X, have definitely written on this subject, there is no need of further counsels from Us. We only beg of you that the writings of those wise pontiffs, and especially Pius X's "Exhortation to the Clergy," should, thanks to your insistent admonitions, not be forgotten, but ever attended to carefully.
"28. There remains one matter which must not be passed over in silence, and that is, to remind the priests of the whole world, as Our most dear sons, how absolutely necessary it is, for their own salvation, and for the fruitfulness of their sacred ministry, that they should be most closely united with their Bishop and most loyal to him. The spirit of insubordination and independence, so characteristic of our times, has, as We deplored above, not entirely spared the ministers of the Sanctuary. It is not rare for pastors of the Church to find sorrow and contradiction where they had a right to look for comfort and help. Let those who have so unfortunately failed in their duty, recall to their minds again and again, that the authority of those whom "the Holy Spirit hath placed as Bishops to rule the Church of God" (Acts xx. 28) is a divine authority. Let them remember that if, as we have seen, those who resist any legitimate authority, resist God, much more impiously do they act who refuse to obey the Bishop, whom God has consecrated with a special character by the exercise of His power. "Since charity," wrote St. Ignatius Martyr, "doth not suffer me to be silent concerning you, therefore was I forward to exhort you, that you run in harmony with the mind of God: for Jesus Christ also, our inseparable life, is the mind of the Father, even as the bishops that are settled in the farthest parts of the earth are in the mind of Jesus Christ. So then it becometh you to run in harmony with the mind of the bishop" (Ep. ad Ephes. iii.). These words of the illustrious Martyr are re-echoed throughout the ages by the Fathers and Doctors of the Church."