The reign of Pope Pius XI fell among some of the most eventful decades of modern history. He is often remembered primarily as a pope who stood up against the persecutions the Church had to suffer at the hands of various anti-Catholic governments in countries as varied as Mexico and Germany. Yet Pope Ratti is rarely brought up for the role he desired to fulfill when he was elected: to be a “pope of the Missions” and which he exercised through nearly two decades with profound effects for the Church around the globe.
Despite the devastation of the First World War, the financial difficulties, and not least the loss of missionary personnel due to the war and its manifold consequences, the Catholic missionary fervor was increasing significantly in the early 1920s. At the same time, Benedict XV’s push for a native hierarchy in the mission countries, a desire expressed in his Apostolic Letter Maximum Illud in 1922, marked an important shift in Church history. Over the following decades, many countries in Africa, Asia and Oceania would not only have their own native bishops, but even cardinals, making the Church ever more visibly a “Universal Church”. Such was the enthusiasm of Benedict XV for the missions that he was soon called “the pope of the Missions” by the public.
Already within the first weeks of his pontificate in early 1922, Pius XI showed the desire to enter into a holy competition with his predecessor. It is reported that he responded those who mentioned the great missionary actions of Benedict XV by saying: “We also want to be called ‘Pope of the Missions’” or “Our predecessor has been called ‘the Pope of the Missions‘; We want to be called so even more”. Over the following 17 years, his teachings and actions in favor of the Great Commission made him arguably the greatest missionary pope of modern times.
Providentially, the year of Pope Pius’ election also marked the 300th anniversary of the foundation of the Congregation de Propaganda Fide, the great governing body charged with organizing the missions ad gentes (now called Congregation for the Evangelization of Peoples). To commemorate this anniversary, the first congress of the Pontifical Missionary Union of priests was held in the week before Pentecost under the presidency of the holy archbishop of Parma, St. Guido Maria Conforti. In a heartfelt address, the pope lauded the work of this priestly union and encouraged it to be introduced in all parishes around the globe. On this occasion, he uttered a sentiment that would become a recurring topic of his missionary thought: that despite the great progress that had been made in the missionary lands, there were still many souls to win for the Savior of the world:
“The Sacred Heart of Jesus, which does not have a more ardent desire than to save souls, has to repeat on the battlefield: Quae utilitas in sanguine meo? Today we feel the truth of these words when we read the statistics. So much pain, so much blood and sweat of the Divine Son; so many centuries since the Redemption, and still so many millions of souls without the fruits of salvation!” 
He repeated this motif when he preached in St. Peter on Pentecost Sunday:
“Much has been done, much has been achieved, many souls have been saved, much glory has been given to God. But how many souls still perish, for how many has the blood of the Redeemer flown in vain! Numerous peoples, in Africa as well as in the vast regions of India and China, are still waiting for the Gospel to be proclaimed.” 
With his characteristic energy and holistic approach, Pius XI dedicated himself to prepare the Church for an effective proclamation of the Gospel. The most far-reaching magisterial act to emphasize the importance of the Catholic missions was the publication of the encyclical Rerum ecclesiae gestarum on 28 February 1926, the first comprehensive missionary encyclical by a Roman Pontiff. According to Msgr. Christian Schreiber, at the time Bishop of Meissen in Germany, Rerum ecclesiae is to be considered as a single teaching along with the famous encyclical on the Social Kingship of Christ, Quas primas . Quas primas teaches Christ’s claim to rule over the entirety of mankind, while Rerum ecclesiae asks all Catholics to propagate the kingship of Christ in the non-Christian nations.
The missionary encyclical can be divided into two parts, one addressed to the clergy and Catholic faithful at home, and the other directed at the missionary superiors in the missions. The pope counts on the “zeal and diligence” of the diocesan bishops to further the interest of the faithful in the missions and to have habitual prayers offered for the missions, as the missionaries’ work will be in vain if “God by His grace does not touch the hearts of the heathen in order to soften and attract them to Himself”. The local ordinaries shall not discourage subjects who feel called to the missions, as God will not leave them without recompense:
“If you deprive yourself of a co-laborer and sharer of your toils, the Divine Founder of the Church will surely supply every such deficiency by showering more abundant blessings on your diocese and by bringing into existence more and more new vocations to the sacred ministry.” (RE, 11)
The Pope is even more forceful in the second part dealing mostly with the topic of the native clergy, commanding missionary superiors to create central institutions in their territories “so that it cannot be said that any native youth has ever been kept out of the priesthood and the apostolate, provided, of course, he exhibits the mark of a true vocation and is a young man of genuine promise.” (24).
In a time in which the intrinsic superiority of the White race was taken for granted by many, Pius XI advocated for racial equality, pointing out that students from the missions often surpass European clerics while studying in Rome. The native clergy should not be considered “lower-grade” priests:
“These priests have been admitted to the same priesthood that the missionaries possess, they are members of the selfsame apostolate. On the contrary, you should prefer the native priests to all others, for it is they who will one day govern the churches and Catholic communities founded by your sweat and labor.” (26)
The fact that Pope Pius XI envisioned the missionary churches to be governed by bishops taken from their own peoples goes hand in hand with a doctrinal development in the best (and only sense) of the word, a deeper understanding of missionary ecclesiology:
“What, We ask, is the true object of these holy missions if it be not this, that the Church of Christ be founded and established in these boundless regions? How can the Church among the heathens be developed today unless it be built of those very elements out of which our own churches were built; that is to say, unless it be made up of people, clergy, and religious orders of men and women recruited from the native populations of the several regions?" (21)
With these teachings, Pius XI heralded a new era in Church history, an ecclesiastical adulthood of sorts for many countries as well as a heightened awareness among all Catholics for the “most Catholic of all enterprises,” as he once called the missions.
The Pope would also lead by example. In June of 1926, he announced in the Apostolic Letter Ab ipsis pontificates primordiis, an addendum to the encyclical, that soon there would be Chinese bishops. Pius XI had identified growing Chinese nationalism as one of the great threats for the missions in China. Nationalist propaganda often depicted the Church as something foreign; Chinese Catholics did not remain unaffected by these claims. In a splendid ceremony, he consecrated six Chinese bishops at the altar of the Throne of St. Peter in St. Peter’s Basilica in Rome on 28 October 1926, the anniversary of his own episcopal consecration. They were the first native bishops from the Celestial Empire since Gregory Luo Wenzao, O.P. (d. 1691), who had been the sole Chinese Catholic bishop to date. In a warm address, the Holy Father spoke of the hope that this consecration would be the first of many such events, and his hopes were well-founded. Only a year later, he personally consecrated the first Japanese bishop, Msgr. Januarius Hayasaka of Nagasaki, at the same altar. By the 1930s, the Archbishops of the Chinese capital of Nanking and that of Tokyo were both native bishops. While there had not been a single native bishop at the beginning of his reign, by his death in 1939, there would be 48, building the base for the first missionary cardinals created under Pius XII.
To fulfill his far-reaching vision, Pius XI could count on a number of enthusiastic collaborators. Perhaps the most important among them was Willem Cardinal van Rossum, C.Ss.R., a Dutch Redemptorist and former consultor to the Holy Office, who was named Prefect of the Congregation de Propaganda Fide under Benedict XV. As Prefect of the Congregation with arguably the most comprehensive prerogatives at the time, it was his task to designate missionary territories and staff them with missionaries, mostly taken from religious congregations. Van Rossum would be one of the pope’s main collaborators in the erection of the native hierarchy. His tenure also saw the creation of the Agenzia Fides, the Vatican news agency focusing specifically on the Catholic missions. One of the most visible testaments to his work is the campus of the Collegium Urbanum (now called Pontifical Urban University) for students of the Propaganda, built in 1926 to accommodate the growing number of alumni from the missionary countries who came to study in Rome.
In China, the missionary region that received much of the paternal attention from Pius XI, the pope was represented by Apostolic Delegate Celso Costantini, who presided the first Plenary Council of China in May and June of 1924 in Shanghai. The event culminated in the consecration of China to Mary, Mother of Grace, at the Shrine of Sheshan. In the face of rising Chinese nationalism, he stressed the supranational character of the Church and pointed out the special interest Pius XI took in China by nominating Chinese bishops. Costantini greatly favored a Chinese style of Catholic art and founded a native congregation, the Disciples of the Lord (Congregatio discipulorum Domini); his beatification process has been opened in recent years. Beyond these great names, the pope could count on a great number of collaborators in various countries, among them the editors of many of the missionary magazines many orders and congregations published.
In summary, the words of Cardinal Salotti spoken in 1932 still hold true today: “In the future, history cannot limit itself to calling Pius XI the Pope of the Missions. It will have to solemnly proclaim that he was the Pope of the most significant missionary development of the past centuries”. This development cannot only be counted in numbers, it was also doctrinal in nature. He emphasized the need for a native clergy, declaring the erection of a native hierarchy as the object of missionary activity. He also demanded the cooperation of all Catholics, priests, and laypeople alike, in the missionary efforts of the Church. While Pius XII created the first cardinals from the missions, something his predecessors could only hope for, it was Pius XI who had paved the way. Cardinal Thomas Tien, China’s first cardinal, was appointed as an Apostolic Prefect in 1934 under Pius XI, making him part of the growing number of native missionary superiors in the Celestial Empire.
The missionary fervor
of Pius XI serves as an example for our times, an example to be studied and
lived by the entire Church, starting with the Pope and including all the faithful
regardless of age and state of life.
 Väth, P. Alfons S.J.: Die Propaganda-Jubiläumsfeiern in Rom. In: Die katholischen Missionen, Herder-Verlagsbuchhandlung, Freiburg 1922
 Schreiber, Dr. Christian: Missionspredigt im Anschluss an die Missionsenzyklika Pius XI. vom 28. Februar 1926. Thema: Unsere Missionspflicht und deren Erfüllung. In: Priester und Mission 1927. Jahrbuch der Unio cleri pro missionibus. Aachener Missionsdruckerei A.G., Aachen 1927