The largest Protestant denomination is the Reformed (Calvinist) Church, with a membership estimated at 780,000 in 1950. The membership of this church is almost entirely Hungarian, and its center is at Cluj, a Calvinist stronghold since the Reformation. Most of the Hungarian aristocracy in Transylvania adopted Calvinism during the Reformation, a period when the Roman Catholic Church was weak in that region. This weakness of the Roman Catholic Church and the political and economic independence of the Transylvanian nobles prevented an effective counterreformation and allowed Protestantism to remain strong in Transylvania while the rest of Hungary was Roman Catholic. Next in size are the Lutherans, with an estimated membership of 250,000 in 1950. Lutheranism is represented by the Evangelical Church of the Augsburg Confession, headed by a bishop at Sibiu, and the Evangelical Synodal Presbyteral Church of the Augsburg Confession, headed by a bishop in Cluj. Membership of both churches is predominantly German. Lutheranism was adopted by the Transylvanian Saxons at the same time that Calvinism was adopted by the Hungarians. In 1938 there were 400,000 Lutherans in Romania; their number was reduced through the loss of northern Bukovina and through the emigration of Saxons to Germany during the 1940s. Continued emigration is further reducing the Lutheran population. The Baptist, Seventh-Day Adventist, and Pentecostal churches were united by government decree in 1950 into the Federation of Protestant Cults. The estimates of the membership at the time of the merger vary greatly, but it probably included between 50,000 and 100,000 Baptists, 15,000 to 70,000 Adventists, and about 5,000 Pentecostals. Before their merger none of these churches had a central organization in Romania, as their congregations were directed from abroad. In the reorganization of theological education in 1948, the Department of Cults assigned one school for church singers and one theological institute for the training of clergy to each Protestant denomination. There was some indication that all denominations had difficulty recruiting young men for the ministry after World War II. After more than a decade of complete isolation from their fellows in other countries, all the Protestant churches resumed an active association with the World Council of Churches in 1961. OTHER RELIGIONS AND CHURCHES