1926, Bučys accompanied Matulaitis-Matulevičius to United States to the 28th International Eucharistic Congress. At the same time, they consecrated a Lithuanian church in Cicero, Illinois, and visited the St Casimir's Lithuanian Church in London. Bučys administered the last rites to Matulaitis-Matulevičius before he died of appendicitis in January 1927. Būčys was elected the new Superior-General in December 1927. In September 1928, he resigned from the university and relocated to Rome. During his tenure as Superior-General until 1933, the Marian Fathers continued to grow and strengthen. The number of members reached 431. New houses were established in Panevėžys, Žemaičių Kalvarija, Rēzekne (Latvia), Washington D.C., and Thompson, Connecticut. Būčys worked to formalize statute, rules, and regulations of the congregation. He represented Lithuania and was elected as honorary member to the committees at the international Eucharistic congresses in Sydney, Australia (1928), Carthage, Tunisia (1930), and Dublin, Ireland (1932). Eastern Catholic mission Before his death, Matulaitis-Matulevičius considered a Catholic mission into Russia. It was supported and encouraged by the Vatican in hopes that respecting and leaving the traditional Byzantine customs would allow implementing Catholic dogma and teaching among Eastern Orthodoxs. After the death of Matulaitis-Matulevičius, Būčys continued to plan the mission. The mission by Michel d'Herbigny proved that a Catholic mission into the Soviet Union was impossible, and the attention was shifted to Russian diaspora. Bishop (also a member of the Marian Fathers), papal internuncio Riccardo Bartoloni, and Prime Minister Augustinas Voldemaras agreed on the mission in Lithuania and the use of the St. Michael the Archangel Church for its purposes. While Lithuanian priests resisted learning Eastern rites and Lithuanian diplomats reconsidered their support due to possible negative effects on relations with Russia, Bučys continued with the mission. From 1929, Būčys was an advisory member of the pontifical commission on Russia. On 6 July 1930, he was consecrated as titular bishop of Olympos by bishop Cyril Kurtev, Apostolic Exarch of the Bulgarian Catholic Apostolic Exarchate of Sofia, at the Church of San Clemente al Laterano. According to traditions, Bučys adopted a new name and chose Petras (Peter). He visited Russian communities in eight countries (including France, Belgium, Yugoslavia) in 1930 and Marian Fathers in United States in 1931. In 1932 and 1933, he visited United States organizing Catholic missions among the Russian immigrants. The Marian Fathers reelected him as their Superior-General in 1933, but the pope would not confirm the results and Bučys was