"The Church of the East (Syriac: ܥܕܬܐ ܕܡܕܢܚܐ ʿĒḏtā d-Maḏenḥā), also called the Persian Church, or the Nestorian Church, was an Eastern Christian church of the East Syriac Rite, based in Mesopotamia. It was one of three major branches of Eastern Christianity that arose from the Christological controversies of the 5th and 6th centuries, alongside the Oriental Orthodox Churches and the Eastern Orthodox Church. During the Early Modern period, a series of schisms gave rise to rival patriarchates, sometimes two, sometimes three. Since the latter half of the 20th century, three churches claim the heritage of the Church of the East.
The Church of the East organized itself in 410 as the national church of the Sasanian Empire through the Council of Seleucia-Ctesiphon. In 424 it declared itself independent of the church structure of the Roman Empire. The Church of the East was headed by the Patriarch of the East seated in Seleucia-Ctesiphon, continuing a line that, according to its tradition, stretched back to the Apostolic Age. According to its tradition, the Church of the East was established by Thomas the Apostle in the first century. Its liturgical rite was the East Syrian rite that employs the Divine Liturgy of Saints Addai and Mari.
The Church of the East, which was part of the Great Church, shared communion with those in the Roman Empire until the Council of Ephesus condemned Nestorius in 431. Supporters of Nestorius took refuge in the Sasanian Persia, where the Church refused to condemn Nestorius and became accused of Nestorianism, a heresy attributed to Nestorius. It was therefore called the Nestorian Church by all the other eastern churches, both the Chalcedonian and non-Chalcedonian, and by the Western Church. Politically the Persian and Roman empires were at war with each other, which forced the Church of the East to distance itself from the churches within Roman territory. More recently, the "Nestorian" appellation has been called "a lamentable misnomer", and theologically incorrect by scholars. The Church of the East itself started to call itself Nestorian, it anathematized the Council of Ephesus and in its liturgy Nestorius was mentioned as a saint. However, the christology of the Church of the East did finally gather to ratify the Council of Chalcedon at the Synod of Mar Aba I in 544.
Continuing as a dhimmi community after the Muslim conquest of Persia (633–654), the Church of the East played a major role in the history of Christianity in Asia. Between the 9th and 14th centuries it represented the world's largest Christian denomination in terms of geographical extent. It established dioceses and communities stretching from the Mediterranean Sea and today's Iraq and Iran, to India (the Saint Thomas Christians), the Mongol kingdoms in Central Asia, and China during the Tang dynasty (7th to 9th centuries). In the 13th and 14th centuries the church experienced a final period of expansion under the Mongol Empire, where influential Church of the East clergy sat in the Mongol court.
Even before the Church of the East underwent a rapid decline in its field of expansion in central Asia in the 14th century, it had already lost ground in its home territory. The decline is indicated by the shrinking list of active dioceses. Around the year 1000, there were more than sixty dioceses throughout the Near East, but by the middle of the 13th century, only one third was left, and after Timur Leng the number was reduced to seven only. In the aftermath of the fragmentation of the Mongol Empire, the rising Chinese and Islamic Mongol leaderships pushed out and nearly eradicated the Church of the East and its followers. Thereafter, Church of the East dioceses remained largely confined to Upper Mesopotamia and to the Saint Thomas Christians in the Malabar coast (modern-day Kerala, India).
Divisions occurred within the church itself, but by 1830 two unified patriarchates and distinct churches remained: the Assyrian Church of the East and the Chaldean Catholic Church (an Eastern Catholic Church in communion with the Holy See). The Ancient Church of the East split from the Assyrian Church of the East in 1968. In 2017, the Chaldean Catholic Church had approximately 628,405 members, the Assyrian Church of the East 323,300, while the Ancient Church of the East had 100,000. This does not consider the St. Thomas Christians, who have also fragmented into several different denominations, including two Catholic and several other Orthodox branches."
Information about the authors of the book "The Oldest Christian People", available below, is provided here. This may help readers to better evaluate the contents of the book.
"William Chauncey Emhardt (January 29, 1874 – August 5, 1950) was secretary of the Episcopal Church's Advisory Commission on Ecclesiastical Relations, and a prominent figure in ecumenical relations between Anglicans and Orthodox Christians, as well as Anglicans and Old Catholics. He was ordained to the priesthood on May 19, 1898 by Bishop Frank Rosebrook Millspaugh, Bishop of the Episcopal Diocese of Kansas.
He received his A.B. from the University of Pennsylvania in 1894, following education at the Episcopal Academy, Philadelphia. He attended the now-defunct Philadelphia Divinity School, which conferred an honorary S.T.D. on him in 1931.
He served as rector of the Trinity Church, Arkansas City, Kansas (assisting at St. John's Military School, Salina, Kansas); Church of the Ascension, Gloucester, New Jersey (1902-1907); St. Luke's Episcopal Church, Newtown, Pennsylvania (1907-1920), and on a number of ecclesiastical commissions. He was the Executive Director of the Foreign Born Division of the National Council of the Episcopal Church."
"George M. Lamsa (Syriac: ܓܝܘܪܓܝܣ ܠܡܣܐ) (August 5, 1892 – September 22, 1975) was an Assyrian author. He was born in Mar Bishu in what is now the extreme east of Turkey. A native Aramaic speaker, he translated the Aramaic Peshitta Old and New Testaments into English. He popularized the claim of the Assyrian Church of the East that the New Testament was written in Aramaic and then translated into Greek, contrary to academic consensus."
No information about the author of the book "The Nestorian Churches" can be found. Information about the author of the "Forward" of the book is provided here:
"Mar Eshai Shimun XXIII (26 February 1908 – 6 November 1975), sometimes known as Mar Shimun XXIII Ishaya, Mar Shimun Ishai, or Simon Jesse, was Catholicos Patriarch of the Assyrian Church of the East from 1920, when he was a youth, until his murder on 6 November 1975. (The difference in regnal numbers depends on which members of the Shimun family one counts as Patriarchs; Mar Eshai chose to use the regnal number XXIII.)
Mar Eshai was born on the 26th of February, 1908 in Qudchanis, the mountainous region located in southern Turkey. Mar Eshai was raised with great care while received the necessary theological and liturgical training by the late Archdeacon of the Patriarch, the Very Reverend Thoma of Ashita and by the Metropolitan of Rustaqa, His Grace, Mar Yosip Khnanishoo, who was also his uncle. At the age of twelve, due to geopolitical upheavals at the time, Mar Eshai was ordained as Patriarch in 1920, succeeding his uncle, Mar Poulus Shimun, XXII. He was educated in England, studying theology at Canterbury and at Westcott House, University of Cambridge. As early as 1926 at the age of 18, the Patriarch attended the Nicene Council Commemoration held at Westminster Abbey, London. The Church and State Conference held in Oxford and the Faith and Order Conference held in Edinburgh were both attended by Mar Eshai in 1937. The distinguished Athenaeum Club of London had bestowed upon Eshai by conferring an honorary membership. He was also a member of the American Historical Society and other organizations as well as being a representative to the World Council of Churches and being notable among the chronicles of Who’s Who. Numerous appeals and publications concerning the Assyrian Question, written by the Patriarch and presented to the British Government and various international bodies, highlight him as a writer of distinction. He was the translator or author of several books on the theology and history of the Church of the East (see "Works" section above.) The volatile political environment and uncertainties for the church caused in 1933 by the independence of Iraq from colonial rule forced the patriarch to be exiled to Cyprus away from the new see in Bebadi. In 1940, he relocated again, to Chicago, Illinois in the United States.
Prior to Mar Eshai Shimun’s intervention, Assyrians living among their Islamic neighbor’s shared a tenuousness relationship that was firmly rooted in mistrust by both sides. Therefore, in 1948 Eshai made a revolutionary announcement of a new policy for the Assyrian people and the Church of the East. Through direct contact to embassy representatives of the Middle Eastern countries in Washington and at the United Nations Headquarters, he broke down the walls of suspicion and misunderstanding. This new policy decreed Assyrians and members of the Church of the East all over the world to remain as loyal and faithful citizens of the countries in which they lived, something that had never been done before.
Mar Eshai became an American citizen about 1949 and settled in the San Francisco area in 1954. In 1964, a dispute over hereditary succession and church calendars caused the metropolitan of the Church of the East in India (known there as the Chaldean Syrian Church) to break away and Mar Thoma was stopped from his duties in the Church of the East. In 1995 Mar Eshai's successor, Mar Dinkha IV, was able to mostly heal the rift. 17% (the Ancient Church of the East) remain separated from the main body of the Church of the East.
Mar Eshai sought to resign as patriarch for health reasons in the late 1960s, but he was persuaded to remain in office. Some activists within the church wanted the patriarch to take a more active role in pushing for a homeland for the Assyrian people, as he had before 1933.
In 1972, Mar Eshai opted to step down from his position as patriarch, and he married the next year. This was controversial, as it contravened longstanding traditions about bishops being able to marry in the Eastern Church.
On a separate track, rumors began circulating with those who consistently went against him decided it was time to have someone new. On 6 November 1975, the patriarch was shot and killed at the door of his home in San Jose, California, by David Malek Ismail, which was a shock to the Assyrian nation, as it was the Malek Ismail family that had protected the Shimun patriarchal line for generations. According to trial records, Ismail said he was upset over the patriarch's marriage; however, the records suggest links between Ismail and church dissidents. According to Deputy District Attorney Brian Madden, the murder of the patriarch Mar Shimun was the outcome of a plot among church dissidents.
When the church council met in London on 17 October 1976, it elected as patriarch Mar Dinkha IV (who had been bishop of Tehran)."