0 To the Patriarchs, Primates, Archbishops, and Bishops of the Catholic World in Grace and Communion with the Apostolic See. When by God's unsearchable design, We, though all unworthy, were raised to the height of apostolic dignity, at once We felt Ourselves moved by an urgent desire and, as it were, necessity, to address you by letter, not merely to express to you Our very deep feeling of love, but further, in accordance with the task entrusted to Us from heaven, to strengthen you who are called to share Our solicitude, that you may help Us to carry on the battle now being waged on behalf of the Church of God and the salvation of souls.
Source: Inscrutabili Dei Consilio (Vatican.va)