"It was around 200 c.e. that Abgar IX adopted Christianity, thus enabling Edessa to become the first Christian state in history whose ruler was officially and openly a Christian."

The fame of Edessa in history rests, however, mainly on its claim to have been the first kingdom to adopt Christianity as its official religion. According to the legend current for centuries throughout the civilized world, Abgar Ukkama wrote to Jesus, inviting him to visit him at Edessa to heal him from sickness. In return he received the blessing of Jesus and subsequently was converted by the evangelist Addai. There is, however, no factual evidence for Christianity at Edessa before the reign of Abgar the Great, 150 years later. Scholars are generally agreed that the legend has confused the two Abgars. It cannot be proved that Abgar the Great adopted Christianity; but his friend Bardaiṣan was a heterodox Christian, and there was a church at Edessa in 201. It is testimony to the personality of Abgar the Great that he is credited by tradition with a leading role in the evangelization of Edessa.

Modern scholars have taken basically two very different approaches to this legend (which obviously reflects the general search for apostolic origins, characteristics of the fourth century), Some would dismiss it totally, while others prefer to see it as a retrojection into the first century of the conversion of the local king at the end of the second century. In other words Abgar (V) the Black of the legend in fact represents Abgar (VIII) the Great (c. 177-212), contemporary of Badaisan. Attractive though this second approach might seem, there are serious objections to it, and the various small supportive evidence that Abgar (VIII) the Great became Christian disappears on closer examination.

"More significant than Bardaisan's conversion to Christianity was the conversion -reported by Bardaisan - of Abgar the Great himself." The conversion is controversial, but whether or not he became a Christian, Abgar had the wisdom to recognise the inherent order and stability in Christianity a century before Constantino did. Ho encouraged it as essential for maintaining Edessa's precarious balance between Rome and Iran. Thus, it is Abgar the Great who lays claim to being the world's first Christian monarch and Edessa the first Christian state. More than anything else, a major precedent had been set for the conversion of Rome itself. // The stories of the conversions of both Abgar V and Abgar VIII may not be true, and have been doubted by a number of Western authorities (with more than a hint at unwillingness to relinquish Rome's and St Peter's own primogeniture?). But whether true or not. the stories did establish Edessa as one of the more important centres for early Christendom."