The Bible is the Christian holy book that missionaries used.
The Bible is the Christian holy book that missionaries used.

For the Roman Catholic Church to have one billion members today, missionaries had to have traveled to many countries over the span of centuries. Dating back as early as the sixth century, the work of Catholic missionaries can be divided into religious orders: Jesuits, Franciscans, Carmelites, Dominicans and Benedictines. Each order's style differed, but they all had one common goal -- to convert as many people as possible to Roman Catholicism.

Jesuits

Also known as The Society of Jesus, the Jesuits were founded in the 16th century by St. Ignatius Loyola who believed that pagan lands such as Asia, Canada and Latin America were in most immediate need of conversion. First, he needed the pope's approval to form the Jesuits as a valid religious order and received initial approval from Paul III in 1540, and final approval from Julius III in 1550. In these papal bulls, Ignatius laid out how the Jesuits would operate: full and total obedience to the pope. Because it was an admittedly drastic reform from how unfaithful he saw people to be, he eased into preaching the message to non-believers. Ignatius also encouraged the Jesuits to blend themselves into the cultures they visited and as a result, the order today has a reputation as skilled linguists and anthropologists, with many of the schools they built still in use.

Franciscans

There are three Orders of the Franciscan movement: the First Order in which ordained men belong to one of three subsects, either the Friars Minor, Friars Minor Conventual or Friars Minor Capuchin; the Second Order, consisting of nuns; and the Third Order, which grouped together laypeople who could not gain access to the first two orders. Based on the teachings of St. Francis of Assisi in the 13th century, the Franciscans lived in large friaries and preached a Catholic life based on obedience, chastity and poverty.

Originating in Rome, the Franciscans moved all over Italy in their missionary work and branched out further to Paris, Oxford, Syria and Africa after St. Francis' death. They preached a life of austerity as being closest to God, and the simplicity of their lifestyle appealed to converts. The schools and friars' houses that the Franciscans built are still found today in Paris and Oxford.

Carmelites

The exact date that the Order of the Brothers of Our Lady of Mount Carmel was founded is uncertain other than it began in the 12th century. They are also divided into three Orders, with the first consisting of the ordained, the second of nuns and the third of laypeople. Members of the Order were originally hermits but grew in number once they started traveling to Cyprus, England, France and Sicily and had success converting non-believers. After Napoleonic rule came to an end with the French Revolution, the Carmelites were able to expand further and settled in Western Europe, the United States, the Middle East and Latin America.

Practicing the rule of St. Albert, the Carmelites' message consisted of love, meditation, poverty and living according to God's will as the most important aim; but it was St. Teresa of Avila who had the most success building friaries and converting people. She preached a message of stricter authority, but balanced that with providing health care to the needy.

Dominicans

Formally known in Latin as Ordo Praedicatorum, the Dominicans had their start in the 13th century at the hands of St. Dominic and are still in existence today. Following the rule of St. Augustine, they preached in three periods: Medieval (13th century to the French Revolution), Modern (French Revolution to 19th century) and Contemporary (19th century to today). Dominicans, known for their intellectual foundation, trained those to be converted in theological education so they would be knowledgeable enough to spread the word of God in an Augustinian manner.

Their long-lasting success can be directly attributed to Dominic himself, as his charisma and articulation enabled him to get his message across clearly and persuasively. He also thought education was of utmost importance and set up schools of theology at every location that he and his followers visited. Although he began his work in Rome, once the Order was sanctioned, he sent his preachers first to France and Spain, and later to Italy, the country where he died.

Benedictines

The oldest and most different of the Catholic Orders, the Order of St. Benedict, also known in Latin as Ordo Sancti Benedicti, was founded in sixth-century England and France by missionaries observing the Rule of St. Benedict (a guide on monastery living that included living humbly, silently and laboriously). Their motto, Ora et Labora (Latin for "Pray and Work") summarizes how they spread Roman Catholicism. Benedictines preached living a life of balance between following the Rule and modifying it to the needs of each individual monastery. In this way, they differ from all the other orders because of the autonomy given to individuals who are allowed flexibility as long as they faithfully observe the spirit of the Rule of St. Benedict.

The Benedictines preached mainly in Italy and Gaul (an area of the Roman Empire that included modern-day France, Belgium, Luxemburg and parts of the Netherlands, Switzerland and Germany). Between the ninth and 12th centuries, the Benedictines managed to build monasteries throughout Western Europe. Much of the appeal of their message lay in the fact that individual communities and monasteries held autonomy and could have been seen as an attractive alternative to the rigid rule that the Catholic Church employed overall.