Aïbeg and Serkis

Aïbeg ("Moon Prince") is thought to have been a Turcophone Christian, possibly Uighur, and Sergis (from the Roman and later Christian name "Sergius" or "Sarkis") a Nestorian Christian, probably Assyrian. Both were sent by Baichu, to accompany the 1245 embassy of the Dominican Ascelin of Lombardia back to Lyon, France, where the Pope was residing at the time. They stayed there for about a year.

Aïbeg and Serkis met with Innocent IV in 1248, and remitted to him a rather vexing letter from Baichu, expressing his difficulty in understanding the Pope's message, and asking for his submission:

As a reply to the letter from Baiju, Innocent IV remitted to the envoys the letter known as Viam agnoscere veritatis. According to historian Kenneth Setton, it "stated that Innocent IV had acted out of a sense of duty to let the true religion be known to the Mongols, and that he regretted the Mongols' perseverance in their errors and adjured them to cease their menaces." The Pope appealed to the Mongols to stop their killing of Christians, while indicating no further interest in continuing the dialogue.