In 1610 Mar Eliyya VIII, entered
communion with the Catholic Church.This created a
situation in which there are two rival claimants approved by Rome,
in one see.He died however in 1617 and his successor
quickly repudiated the union.
reign of Mar Shimun XXIII, in 1964, a schism appeared in the
Assyrian Church of the East causing the establishment of a separate
Ancient Church of the
East with its center in Baghdad in 1968 and
a rival catholicos-patriarch Mar Thoma
Darmo assigned, while Mar Shimun XXIII continued as the
official head of the Assyrian Church of the East.The rift was healed in 1995, thanks to H.H.Mar Khanania Dinkha IV,
though a small group continues to follow the Ancient Church of the
East as separated from the main body of the Church of the East.