In the 9th century, during theArab–Byzantine wars, theByzantine Empire used asemaphore system ofbeacons to transmit messages from the border with theAbbasid Caliphate acrossAsia Minor to the Byzantine capital,Constantinople.
According to Byzantine sources (Constantine Porphyrogenitus,Theophanes Continuatus andSymeon Magister), the line of beacons began with the fortress ofLoulon, on the northern exit of theCilician Gates, and continued with Mt. Argaios (identified mostly with Keçikalesı onHasan Dağı, but also withErciyes Dağı nearCaesarea), Mt. Samos or Isamos (unidentified, probably north ofLake Tatta), the fortress of Aigilon (unidentified, probably south ofDorylaion), Mt. Mamas (unidentified, Constantine Porphyrogenitus hasMysian Olympus instead), Mt. Kyrizos (somewhere betweenLake Ascania and theGulf of Kios, possibly Katerlı Dağı according toW. M. Ramsay), Mt. Mokilos abovePylae on the southern shore of theGulf of Nicomedia (identified by Ramsay with Samanlı Dağı),Mt. Saint Auxentius (modern Kayış Dağı) south-east ofChalcedon (modern Kadıköy) and the lighthouse (Pharos) of theGreat Palace in Constantinople.[1][2] This main line was complemented by secondary branches that transmitted the messages to other locations, as well as along the frontier itself.[3]
The main line of beacons stretched over some 720 km (450 mi). In the open spaces of centralAsia Minor, the stations were placed over 97 km (60 mi) apart, while inBithynia, with its more broken terrain, the intervals were reduced to ca. 56 km (35 mi). Based on modern experiments, a message could be transmitted the entire length of the line within an hour.[3] The system was reportedly devised in the reign of EmperorTheophilos (ruled 829–842) byLeo the Mathematician, and functioned through two identicalwater clocks placed at the two terminal stations, Loulon and the Lighthouse. Different messages were assigned to each of twelve hours, so that the lighting of abonfire (seefire beacon) on the first beacon on a particular hour signalled a specific event and was transmitted down the line to Constantinople.[2][3]
According to some of the Byzantine chroniclers, the system was disbanded by Theophilos' son and successor,Michael III (r. 842–867) because the sight of the lit beacons and the news of an Arab invasion threatened to distract the people and spoil his performance as one of thecharioteers in theHippodrome races. This tale is usually dismissed by modern scholars as part of a deliberate propaganda campaign by 10th-century sources keen to blacken Michael's image in favour of the succeedingMacedonian dynasty.[4][5] If indeed there is some element of truth in this report, it may reflect a cutting-back or modification of the system, perhaps due to thereceding of the Arab danger during Michael III's reign.[3] The surviving portions of the system or a new but similar one seem to have been reactivated underManuel I Komnenos (r. 1143–1180).[3]