Roman Christian missions that began in the 5th century were closely associated with military-political expansion. Christianization as a phenomenon was promoted through an aggressive foreign policy rather than peaceful interaction. Tucker argues that during this period, the basic foundations of missionary work were born with an emphasis on targeted work with the Gentiles and the destruction of their pagan idols. Individual religious representatives, for instance, Gregory the Great, implemented the decrees of the Roman Catholic Church and contributed to introducing Christianity in new regions, including both European countries and the eastern direction. According to Tucker, in the 9th century, missionary activities reached China, Korea, and Japan, but they lasted until the 13th century and fell into decay under the influence of more aggressive Islamic conquerors. Nevertheless, during the Middle Ages, the flourishing of the Roman Catholic Church took place, and at the behest of the Vatican, the propaganda work continued successfully.
Roman Christian missions would not have been sufficiently effective without the involvement of individual missionaries dedicated to educating the Gentiles. Tucker mentions the contributions of the Englishman Boniface, the Scandinavian Ansgar, the Spaniard Raymond Lull, and several other prominent figures. Each of them conducted missionary work in different ways, but they all came to the conclusion that their life purpose was to advance the doctrine of God and his greatness. Fighting heretics and trying to convey the importance of observing biblical norms and traditions became the key ideological trends of the representatives of the theological movement. Therefore, due to the work of individual missionaries, the success of the Roman Catholic Church in promoting Christianity and establishing a single dominant religion may be considered achieved.