This put them into conflict with two other "Byzantine offshoots" that had been formed: the Empire of Nicaea in western Anatolia, ruled by Theodore I Laskaris, and the Despotate of Epirus in Greece, ruled by Michael Comnenos Doukas.
Trebizond also had continual concerns about the Turks, first the Seljuks and then the Ottomans, as well as Constantinople—wanting to bring Trebizond back under its wing—and the Republic of Genoa, who wanted more control of trade on the Black Sea. One of the ways to deal with potential (and actual) hostility was for the emperors of Trebizond to make marital alliances by matching their daughters with foreign nobles. Emperor Alexios IV (1417 - 1429) married two daughters off to two khans of neighboring Muslim empires, and an another daughter to Byzantine Emperor John VIII Paleologos. John II of Trebizond married Eudokia Paleologina, daughter of Byzantine Emperor Michael VIII Paleologos to keep friendly with Constantinople.
The Turkish threat never ended, however, and increased when Osman I of Anatolia and his successors consolidated their people into what became known as the Ottoman Empire. This empire rapidly encompassed the Eastern Mediterranean and the Black Sea countries, and more. When they conquered Constantinople on 29 May 1453, Byzantine culture was overwhelmed. Trebizond realized it would not long last if the Byzantine Empire had been conquered. The penultimate Trebizond emperor, John IV (1429 - 1459), saw the writing on the wall. He sent a message to Florence, offering a union of Roman Catholic and Orthodox Churches to forge an alliance that would provide him aid, but it did not help. He gave his daughter to another khan to try to gain military aid. He asked Georgia for help. None of this would be sufficient.
John's brother David Megas Comnenos came to power in 1459. Trebizond fell completely to the Ottomans in 1461. He and his family were taken to Constantinople, the new Ottoman capital. He and all male members of the family were executed in 1463.
So who were the Ottomans who conquered so much of the world and threatened Western Europe? Let's find out tomorrow.