The Empire of Trebizond
Trebizond, a Byzantine successor state, owed most of its tenuous existence to the contemporary belief that its princesses were of unsurpassed beauty. Leaders of the surrounding hostile Turkoman federations, Ak Koyunlu in particular, would line up for their hands in marriage, in exchange for allowing Trebizond to exist. This, combined with generous tribute payments, allowed it to curiously endure for over 250 years, a thin strip of land hugging the south-eastern Black Sea coast, surrounded entirely by enemies.
Founded and run by the Byzantine Komnenus family in 1204 in the aftermath of the Fourth Crusade, Trebizond harboured a small Greek island of culture, rarely counting over 10,000 people; yet due to its position as a Western terminus of the Silk Road, the "Empire" was wealthy disproportionate to its numbers. Medieval Trebizond was a flourishing centre of science and the arts, being a repository of translated Arabic & Persian texts, and left behind huge, richly painted monasteries and churches. Their imposing Soumela Monastery, perched high on a forested mountain and containing lush artwork and frescoes, still exists today. The emperors, in another stroke of luck, were endowed with numerous princesses and few princes, which helped keep the succession struggles that paralyzed their Byzantine cousins manageable.
The little Empire actually outlived the Byzantines, ending in 1461 when then-Emperor David overplayed his hand. Believing he had successfully tempted the Burgundian duke and the Pope into an anti-Ottoman league, and cobbling together the surrounding little emirates through royal marriage, David had the temerity to ask Ottoman Emperor Mehmed The Conqueror for a refund on some of the tribute he'd paid them. A short war later, Trebizond was captured, and David and three of his sons were beheaded. It was the last self-governing Greek state until Greece's own independence in 1829.