The city of Sinope in Anatolia was a major port and a key part of the Black Sea trade network, it had strong trade relations with the Crimea. It thrived during the centuries of Arab raids as it lay outside their typical raiding area, even though it was attacked in 858. It was part of the key areas of coastal and western Anatolia which was the economic core of Asia Minor.
In 1081 the Seljuks captured the city along with a regional treasury there, just as they had most of Anatolia after Manzikert. However, Emperor Alexios Komnenos was able to liberate Sinope and return it to imperial rule. During the Komnenian era it thrived once more as an important and well-defended fortified trade city.
After the Fourth Crusade, the breakaway Empire of Trebizond captured Sinope, briefly from 1204-1214. The Seljuks captured Sinope from the Empire of Trebizond and held it until 1254, when Trebizond retook it for 11 years. After 1265 it remained under consistent Turkish control.
SOURCES:
The Oxford Dictionary of Byzantium by Alexander Kazhdan
shadowsofconstantinople.com 