According to some historians, the village of Biertan was attested in 1224, in a diploma issued by King Andrew of Hungary. Biertan was then a part of the Two Seats Saxon administrative unit. At that time, Biertan was competing with Medias and Moşna to claim the residence title for these seats. The Saxon inhabitants of Biertan were settlers from the Franconia area of Germany. Biertan had lined up houses built around a central square, with the church-fortress located in the middle. Biertan had suffered during the great Mongol Invasion of 1241. This prompted its inhabitants to become involved in the Christians’ efforts of constructing a series of stone fortresses to stave off Mongol invasions. In Biertan, the locals raised three rows of walls, reinforced with 6 towers and 3 bastions, which turned the church-fortress into one of the strongest fortifications in southern Transylvania. The settlement prospered, and as a sign of their wealth, the Biertan Saxons decided to rebuild the church in the centre, and dedicate it to Saint Mary. The construction was carried out between 1486 and 1524, following a late Gothic style. The three naves church in Biertan is the last of its kind built in Transylvania. The Saxons had hoped that they would acquire their own ecclesiastical hierarchy, given the almost permanent state of conflict between the Saxon clergy and the Roman Catholic Bishop of Alba Iulia. The failure to receive a proper bishop from the Catholic Church only encouraged the Saxons to adopt the religious reform. Biertan took full advantage of this phenomenon.