There was a group from the Assyrian Church of the East that converted to the Orthodox Church in 1898. "In the mid 1890's, Abun Mar Yonan, the Nestorian Bishop of Urmia, petitioned the Holy Synod of the Russian Orthodox Church that he and his flock be received into the Russian Church. Mar Yonan traveled to Saint Petersburg in 1898, where he and several of his clergy accepted Orthodoxy. They were received into the Russian Orthodox Church by confession of faith and vesting on the Feast of the Annunciation at the Holy Trinity Cathedral in Saint Alexander Nevsky Lavra. The services were presided over by Metropolitan Pallady (Raev) of Saint Petersburg ... Also in 1898, the Holy Synod of the Russian Orthodox Church established the Russian Ecclesiastical Mission in Urmia, in order to aid Mar Yonan in the conversion and education of his flock." http://www.roca.org/bishop_john.htm
Along with Bishop Yonan, Archimandrite Elia (Abraham) converted to Orthodoxy in 1898; after the death of Bishop Yonan, he was consecrated to the Episcopate and succeeded Bishop Yonan. After the Russian Revolution, Bishop Elia could no longer communicate with Patriarch Tikhon in Moscow, and joined the Russian Orthodox Church Abroad. Bishop Elia died in 1928, and he was succeeded by Bishop John (Gewarigis) who was consecrated to the Epicopate in Belgrade in 1931 by Metropolitan Antony (Khrapovitsky) and Archbishop Germogen (Maximov).
"In 1918, he was part of the exodus of Christians- Orthodox, Armenians, Uniates, and Protestants alike-from northern Persia due to renewed persecution by the Moslems. Over 100,000 Christians fled northern Persia heading south to Iraq; untold numbers were massacred along the way. The Orthodox Assyrians eventually ended up in Baghdad. The future Bishop John almost immediately returned to Urmia, to attend to those Orthodox Assyrians who had stayed behind.
Bishop John resided in Baghdad where most of his flock lived. He retired due to old age in 1945, and eventually made his way to the U.S., where he lived with his son in Chicago. In the early 1950's, Bishop Nikon (Rklitsky, later Archbishop of Washington and Florida), while visiting Chicago, "had a wonderful meeting with Bishop John of Urmia and Salma, the eldest member of our Council of Bishops, and spiritual head of the Orthodox Assyrians." Vladika Nikon noted that Bishop John spoke the same language as that spoken by Christ the Savior, and had been the translator at the Russian Ecclesiastical Mission in Urmia. After moving to Chicago to live in retirement, he found there were several thousand of his fellow Orthodox Assyrians, who were spiritually undernourished, living in the Chicago area. When Vladika Nikon visited Bishop John, he found him "surrounded by Americans of Assyrian origin," to whom Bishop John was reading the Bible in their native language. The Synod of Bishops, through Archbishop Gregory (Borishkevitch) of Chicago and Cleveland (later of Chicago, Detroit and Midwest America), Protopresbyter Arkadii Tsepuro, Protopresbyter George Grabbe (later Bishop Gregory of Washington & Florida), and Protopresbyter Adrian Rymarenko (later Archbishop Andrei of Novo Diveyevo) arranged for Bishop John to live in retirement at the Novo Diveyevo Convent in Spring Valley, New York. He reposed at Novo Diveyevo in 1960 at the age of 105, and is buried in the cemetery located there." http://www.roca.org/bishop_john.htm
"Bishop John (Gevargizov) of Urmia & Salma, 1855-1960"
For the complete story of the conversion of the Orthodox Assyrians in 1898, see:
Abramtsov, Father David
'The Assyrians of Persia and the Russian Orthodox Church'
No. 6, 1960
Also interesting, concerning the Assyrians:
The Church of the East and the Church of England: A History the Archbishop of Canterbury's Assyrian Mission
Oxford, England 1992
The Foreign Missions of the Russian Orthodox Church
London, England 1943