Although Christianity--Roman Catholicism and Protestantism--was the most rapidly growing religion in Indonesia in the 1980s, its numbers were small compared to Islam (9 percent of the population compared to 86.9 percent Muslim in 1985). Christianity had a long history in the islands, with Portuguese Jesuits and Dominicans operating in the Malukus, southern Sulawesi, and Timor in the sixteenth century.
When the Dutch defeated Portugal in 1605, however, Catholic missionaries were expelled and the Calvinist Dutch Reformed Church was virtually the only Christian influence in the region for 300 years. Whereas the United East Indies Company (VOC) was primarily a secular and not a religious enterprise, and because Calvinism was a strict, austere, and intellectually uncompromising variety of Christianity that demanded a thorough understanding of what, for Indonesians, were foreign scriptures, Christianity advanced little in Indonesia until the nineteenth century.
Only a few small communities endured in Java, Maluku, northern Sulawesi, and Nusa Tenggara (primarily Roti and Timor). After the dissolution of the VOC in 1799, and the adoption of a more comprehensive view of their mission in the archipelago, the Dutch permitted proselytizing in the territory. This evangelical freedom was put to use by the more tolerant German Lutherans, who began work among the Batak of Sumatra in 1861, and by the Dutch Rhenish Mission in central Kalimantan and central Sulawesi. In addition, Jesuits established successful missions, schools, and hospitals throughout the islands of Flores, Timor, and Alor.
The twentieth century witnessed the influx of many new Protestant missionary groups, as well as the continued growth of Catholicism and of large regional and reformed Lutheran churches. Following the 1965 coup attempt, all nonreligious persons were labelled atheists and hence were vulnerable to accusations of harboring communist sympathies. At that time, Christian churches of all varieties experienced explosive growth in membership, particularly among those people who felt uncomfortable with the political aspirations of Islamic parties.
In the 1990s, the majority of Christians in Indonesia were Protestants of one affiliation or another, with particularly large concentrations found in Sumatra Utara, Papua, Maluku, Kalimantan Tengah, Sulawesi Tengah, and Sulawesi Utara. Catholic congregations grew less rapidly in the 1980s, in part because of the church's heavy reliance on European personnel. These Europeans experienced increasing restrictions on their missionary activities imposed by the Muslim-dominated Department of Religious Affairs. Large concentrations of Roman Catholics were located in Kalimantan Barat, Papua, Nusa Tenggara Timur, and Timor Timur provinces.