Napata to further downstream, where the fortress of Dongola, the new seat of the royal court, was founded and which soon developed a vast urban district. Many more fortresses were built along the banks of the Nile, probably not intended to serve a military purpose, but to foster urbanization. Already at the time of the foundation of Dongola contacts were maintained with the Byzantine Empire. In the 530s, the Byzantines under Emperor Justinian mounted a policy of expansion. The Nubians were part of his plan to win allies against the Sasanian Persians by converting them to Christianity, the Byzantine state religion. The imperial court, however, was divided in two sects, believing in two different natures of Jesus Christ: Justinian belonged to the Chalcedonians, the official denomination of the empire, while his wife Theodora was a Miaphysite, who were the strongest in Egypt. John of Ephesus described how two competing missions were sent to Nubia, with the Miaphysite arriving first in, and converting, the northern kingdom of Nobatia in 543. While the Nobatian king refused Justinian's mission to travel further south archaeological records might suggest that Makuria converted still in the first half of the 6th century. The chronicler John of Biclar recorded that in around 568 Makuria had “received the faith of Christ”. In 573 a Makurian delegation arrived in Constantinople, offering ivory and a giraffe and declaring its good relationship with the Byzantines. Unlike Nobatia in the north (with which Makuria seemed to have been in enmity) and Alodia in the south Makuria embraced the Chalcedonian doctrine. The early ecclesiastical architecture at Dongola confirms the close relations maintained with the empire, trade between the two states was flourishing. In the 7th century, Makuria annexed its northern neighbour Nobatia. While there are several contradicting theories, it seems likely that this occurred soon after the Sasanian occupation of Egypt, presumably during the 620s, but before 642. Before the Sasanian invasion, Nobatia used to have strong ties with Egypt and was thus hit hard by its fall. Perhaps it was also invaded by the Sasanians itself: some local churches from that period show traces of destruction and subsequent rebuilding. Thus weakened, Nobatia fell to Makuria, making Makuria extend as far north as Philae near the first cataract. A new bishopric was founded in Faras in around 630 and two new cathedrals styled after the basilica of Dongola were built in Faras and