He all but destroyed Zoroastrianism and Manichaeism in China, and his persecution of the growing Nestorian Christian churches sent Chinese Christianity into a decline from which it never recovered.
As Nestorianism had its roots in the Antiochene tradition and was opposed by the Alexandrian tradition, Christians in Syria and Egypt who wanted to distance themselves from the extremes of Nestorianism and wished to uphold the integrity of their theological position adopted this term to express their position.
In 431 he tried, unsuccessfully, to place Saturninus on the episcopal throne of Marcianopolis in place of the Nestorian Dorotheus.
This comprised most of the upper basin of the Great Zab, with the country of the Nestorian Christians and many districts inhabited by Kurdish tribes, some of them large nomad tribes who descended for the winter to the plains of the Tigris.