The Aydinids also held parts of the port of Smyrna (modern İzmir) all through their rule and all of the port city with intervals. Especially during the reign of Umur Bey, the sons of Aydın were a significant naval power of the time. The naval power of Aydin played a crucial role in the Byzantine civil war of 1341–1347, where Umur allied with John VI Kantakouzenos, but also provoked a Latin response in the form of the Smyrniote crusades, that captured Smyrna from the beylik.