Osroene

Osroene, the kingdom of Edessa, was the Arab buffer state of Upper Mesopotamia, lasting from 132 BC to 214 AD. When Seleucid power broke, Nabataean Arab chiefs of the Abgarid house seized Edessa, today's Şanlıurfa, and built a caravan kingdom on the Euphrates crossing, allied with Parthia and rich on trade. The Abgars played the two superpowers with desert patience for three centuries: bowing to Rome in 114, rebelling, rebowing, lending archers to emperors and daughters to kings. Edessa's fame outgrew its size: in 201 its king made Christianity the state religion, the first kingdom on earth to do so, and its Syriac schools and the legend of Christ's letter to King Abgar drew pilgrims for a thousand years. Rome tired of the game in the third century, stripped the last Abgar, and folded Osroene into a province, finally in 244. The buffer became a highway, and Edessa's lamps passed from kings to bishops.