For centuries they maintained missions in Tartary, China, and other eastern regions.

Their churches were scattered from Syria and Cyprus to Pekin, and from the coast of Malabar and Ceylon to the borders of Siberia.

Early in the eleventh century, Unkh Khan, a Tartar prince on the northern borders of China, invited Nestorian missionaries among his people, and himself became the famous Prester John.

Gengis Khan and several of his sons and grandsons, who conquered China and almost all Asia and a part of Europe, were connected with Prester John by marriage.

Several of them had Christian wives, and one of them at least professed himself a Christian.