« RERUM ECCLESIAE ». — Thus begins the encyclical letter of Pius XI dated 28 February 1926, intended to recall in writing the teachings of the Vatican Missionary Exhibition of the Holy Year 1925 (Sylloge de Propaganda Fide, Roma 1909, no. 120, pp. 240–258).
In the introduction, the Holy Father states that the Church, though with varying success, has always sought to win for Jesus Christ those who were far from him; he then recalls the beneficial effects of Benedict XV’Maximum illud (v.), the Vatican Missionary Exhibition, and the establishment of the Lateran Missionary Museum, and, noting with sorrow that many infidels still remain, admonishes all Christians concerning their duties in this matter and asks for their generous assistance. The first part of the encyclical speaks of the missionary duty in general, which it grounds in the virtue of charity, and of the particular missionary duty, which consists chiefly in praying for the missions and in awakening and cultivating vocations to the apostolate. For this purpose, it recommends that Missionary Union of the Clergy (v.) and the three Pontifical Missionary Societies (v.) be established and organized in every diocese. The second part reminds mission superiors of the duty to form a numerous and capable indigenous clergy by founding seminaries, and to instruct catechists well. It recommends the establishment of indigenous religious congregations and the introduction of contemplative Orders. It then gives precise directives on how to distribute missionary forces in order to follow the strategy of a progressive conquest of the territory.
Finally, Pius XI recommends that, in the event of a shortage of missionaries, the Ordinaries of missions call new workers, including from other religious families. He also reminds religious Congregations that the territories are entrusted to them at the pleasure of the Holy See, which may freely assign them to other institutes, divide them, and entrust them to the indigenous clergy or to other Congregations. Lastly, he exhorts all bishops to assist the missions by the means suggested.
« EVANGELII PRAECONES ». - This missionary topic is also addressed in the encyclical Evangelii praecones of Pius XII, dated June 2, 1951 (AAS, 43 [1951], pp. 497-558), which may be divided into three parts.
The first part, following a brief introduction explaining the occasion that prompted the publication of the encyclical, discusses the progress achieved over the past twenty-five years in terms of the number of conversions, the ecclesiastical organization of various territories, and the structuring of missionary collaboration. It then recalls that in some regions of Asia persecution is raging and how much
remains to be accomplished in the field of apostolate. In the second part, after offering some suggestions on missionary methodology, describing the figure and preparation of the missionary, it states that the purpose of missions is to establish the Church therein, and thus in newly conquered territories to raise and prepare a numerous and capable indigenous clergy; to organize Catholic Action, to erect all various religious and charitable works, to multiply schools, to promote the press, and especially to address the social question according to Catholic principles. In all this apostolic activity, the missionary must never forget the principles of a sound adaptation to the customs and traditions of the peoples. The third part, after mentioning the fruits obtained from the Exposition of the Holy Year of 1950, recommends the missionary union of the clergy, the other pontifical missionary works, as well as apostolic work, and concludes by exhorting the clergy and the faithful to generously assist the work of the Catholic apostolate.