Our knowledge of Byzantine ships remains limited due to the relatively little and scattered in various manuscripts information on the subject, also to the de facto absence of a systematic monograph on this topic.
Furthermore, it is obvious that ships were not at all a source of inspiration to artists of the Bosphorus as opposed to earlier and later painters, whose representations combined with documents of the time supply us with important information on ships.
However, the fact is that during the iconoclastic period (723-843 AD) the representation of ships on icons was strictly forbidden and as a result we know almost nothing about these years.
Nevertheless, on the basis of a little, scattered information, we can reach the conclusion that the historic circumstances prevailing in mediaeval times contributed to the application of many changes and innovations to shipbuilding both in Byzantium and in the Eastern Mediterranean.This influence proved crucial to the thereafter evolution and development of the sailboat. We do not intend to number or examine all these changes and innovations, still we will mention as examples the substitution of the rudder for the wheel, an invention which in all probability must be credited to the Arabs, also, the evolution of square sails, a sailing device which has made possible the building of larger ships. However, we will be more thorough on an important change, the development, that is, during this period, of the already existing type of the triangular sail, but in large dimensions,so as to function properly on large vessels.