Introduction 
  'CATHOLICOS OF THE EAST' was originally  the title  conferred to  the ecclesiastical head of the Christian congregation in the erstwhile Persian  Empire that extended from Mesopotamia in the west, to the boundaries of the  present day Afghanistan and Northern India in the east. In the beginning the bishop who assumed this title  was known as MAJOR METROPOLITAN / CATHOLICOS OF SELEUCIA; Seleucia being the  capital city of Persian Empire. This institution was initially set up to serve  as a link between the Patriarch of Antioch, and the Syrian Christian Community  in Persia  who found the journey to the Patriarchate at Antioch,  hazardous because of the bitter political rivalry between the Roman and Persian  empires. 
  The Church in Persia was known in different  names: Persian Church, Babylonian Church, East Syrian Church, Church of East,  Chaldean Church etc. Though the jurisdiction of the Seleucian Catholicate was  initially within the Persian Empire only, it later extended to few other regions  outside the empire in Asia in the further East, through missionary activities. 
  
  Catholicos/Maphryono  (Maphrian) 
       The term  ‘Catholicos’ (Katholikos) is derived from the Greek words ‘Kath-Holikos’,  meaning ‘General Primate’ or ‘General Vicar’. Even before  the primates of the Church adopted this title, it existed in the Roman Empire  where its Government representative who was in charge of a large area was called  ‘Catholicos’. The Government servant, who was in charge of State treasury, too  was known by that name. In due course, the secular administrative heads in  Persian Empire also adopted this title.     
  The Churches  (mainly outside the Roman Empire) started to use this term for their Chief  Bishops much later, probably by 4th or 5th centuries.  Now  the primates of the Orthodox Churches in Armenia, Georgia, Iraq and India, use  the title ‘Catholicos’. 
  ‘Maphryono’ (Maphrian) is derived from the Syriac  word afri, “to make fruitful’, or "one who gives fecundity". This title  came to be used exclusively for the head of the Syrian Orthodox Church in the  East (Persia) after  the prelates who occupied the office of the Catholicate since late 5th century  adopted Nestorian Christology and separated from the mother Church. From the mid  13th century onwards, a few occupants of the Maphrianate were referred also as  ‘Catholicos’, but the title never came into extensive usage. However in the 20th  century when this office of the Maphrianate under the Holy See of Antioch was  established in India,  the chief of the local church assumed the title ‘Catholicos’. It is this title  that is being used in India today, while the title ‘Maphryono’ (Maphrian) is no  longer used.
   
  Evolution of the  historic office of Catholicos of the East 
       At the dawn of Christianity in the 1st century, there were  two great political powers that stood against each other in the Near and the  Middle East; the Roman (Byzantine) Empire and the Empire of the Parthians (or  Sassanaid Persians since the early 3rd century), the traditional enmity of which  has a determining influence on the history of that area for centuries. The  border line between these rival empires divided the landscape of Mesopotamia with the Syriac  speaking population on either side. The great city of Antioch where a Christian  presence appeared for the first time outside Palestine, was the capital of the  Syrian Province, in the Eastern part of the Roman Empire. The bishoprics of the  city of Antioch have special importance in the history of Christianity as it was  here St. Peter, the chief of the Apostles, established his Apostolic See in AD  37.  Antioch and regions east of it were placed under the care of the  Bishop/Patriarch of Antioch and all the East. (The Christian church laws that  took shape in the early era through regional and ecumenical councils reaffirmed  the ecclesiastical jurisdictions of the Patriarchs of Antioch, Alexandria and Rome). 
  But the political barriers between the Persian and Roman  Empires and the bitter rivalry of its rulers made intercommunications between  the two regions much more difficult and dangerous. There were instances where  clergy from Persia  who were ordained by the Patriarch of Antioch were put to death alleging to be  spies.  It therefore, became necessary for the Patriarch to vest authority in an  ecclesiastical dignitary to carry on the administration in the Persian region.  Thus evolved the historic office of the  Catholicate in Seleucia  (Persian capital).  The Bishop/Catholicos of Seleucia acted as the deputy of  the Patriarch of Antioch, in the Persian Empire, with some exclusive privileges to consecrate  bishops on behalf of the Patriarch. Though attempts to bring the Church under  this single authority (Seleucian bishop) started in early 4th century itself, it  became fruitful only a century later.  Initially the other prelates of Persia were opposed to the  idea of vesting powers in this Catholicate, but the support from the Antiochean  Patriarchate helped to shed all barriers.
   
  The First    Catholicos of the Syrian Church 
       It was around the year 300, an attempt was made  for the first time to establish the Church in the Persian Empire in  an organised form.  The initiative for this was taken by Bishop Papa  (Baba,  AD.267-329) of the Persian royal capital at Seleucia-Ctesiphon with  the consent of the Patriarch of Antioch.  In AD 315, the Bishop convened a Synod  of the Persian prelates at Seleucia  in which he tried to organize the local churches, with himself as a head.  But  the other prelates, especially those of Persia proper resisted and even deposed  Bishop Papa.  At this crucial juncture, the Bishops of Antioch, Edessa and  Nisibis came to his rescue and reinstated him as prelate of the prime city.    
  It is believed that the title 'CATHOLICOS' was  first used by this Bishop Papa.  Anyhow,  neither  this  Seleucian  bishop nor  his successors, until 410, never had  any  authority over other   bishoprics  in Persian empire and hence the title Catholicose, if ever used by Bishop Papa,  does not mean in the same sense as it  was  known later. 
  About a century after, another serious attempt was made to  unite all the bishoprics in the Persian Empire.  In AD 410, an historic Synod of the churches in Persia  was   held under the auspices of Bishop Mor  Marutha  of Muipharqat (delegate of the Antiochean Patriarch),  which recognized the primacy of the Metropolitan of Seleucia for the first time.   Thus MOR ISHAQ (Issac), the bishop of  Seleucia  becomes the head of the Persian Church.  He is the one who is acknowledged as  the first "CATHOLICOS", with jurisdiction over the entire Persian Empire.   He   assumed this  title at the Synod of Seleucia held in AD 410.  The primate at that time, was also conferred with  the title "Great Metropolitan and Chief of All Bishops". (In some other records  the title is mentioned as "Great Metropolitan of All the East and Major  Metropolitan of Seleucia-Ctesiphon".) 
       
   Churches that claim the   succession from   the  Catholicate of the East 
       From the days  of establishment of Christianity in  Persia,  the Church there had to face severe  persecutions;  first from the Parthian  and   Persian kingdoms  that considered the Christians as  their  adversaries, then due to the dissidence grown within their congregations and  because of crusades,  finally on account of the Moslem and Mongolian  aggressions.  Thus  the Syrian  Church in Persia/East   separated into three main stream Churches  with two more sub-divisions in the last century.  The lists  of the Syriac Churches in the East that are under separate Catholicates are  given below.
             
   
    {1}   CATHOLICATE  OF THE SYRIAN ORTHODOX (JACOBITE) CHURCH 
                                            OF ANTIOCH AND ALL THE EAST
               (Orthodox)
                                   In the early centuries the Christians in the Persian and  the Roman Empires were subject to religious persecutions, so the Church spread  its wings without the help of any of the imperial authorities.  After the Roman  Emperor accepted Christianity in 315, the church in Rome  was spared from atrocities, but from then onwards the Persian rulers adopted a  much more hostile attitude towards those Christians in Persia as they were  considered as agents of the former.  It was during this period that the office  of the Great Metropolitan, which later came to be known as the Catholicate of  East, was established in Persia.  As the enmity between the empires increased,  the leaders of the Church in Persia found it nearly impossible to continue  ecclesiastical commune with the universal Church.  Meanwhile some in the  Catholicate of Persia found it more convenient to adopt the Nestorian  Christology which was earlier officially rejected by the universal Christian  councils for its remarks on the Mother of God; thus they tried to convince the  Persian rulers that they distance themselves from the mother Church and the  Roman (Byzantine) Empire.  By this act, the Christians in Persia who accepted  Nestorian Christology could easily win the favour of the Persian rulers while  those of non-Nestorian faith suffered severe persecution.  As  the office of the Catholicate fell into heresy, the Orthodox faithful were  wandering in wilderness.  The Catholicos of Seleucia meanwhile took over  the title 'Patriarch', thus trying to be equal in status with the Patriarch of  Antioch. 
  Even though the Church in Persia had officially  accepted Nestorius as a Church father, a substantial group of Christians in  Mosul, Niniveh and Tigris (Tagrit) continued to keep their loyalty to the old faith.  A few decades later the Orthodox wing of the Church in Persia that continued to be under  the Syriac Orthodox Patriarchate of Antioch & all the East,  got reorganized under St. Ya`qub Burdono and installed St. Ahudemmeh as 'The  Great Metropolitan of the East', but he too found it difficult to discharge his  ecclesiastical duties smoothly.  However by the 7th century the situation  changed for better which finally led to the formation of an office of the 'Maphrianate  of the East’ at   Tigrit  (Tagrit).
  Church in Persia that continued to be under  the Syriac Orthodox Patriarchate of Antioch & all the East,  got reorganized under St. Ya`qub Burdono and installed St. Ahudemmeh as 'The  Great Metropolitan of the East', but he too found it difficult to discharge his  ecclesiastical duties smoothly.  However by the 7th century the situation  changed for better which finally led to the formation of an office of the 'Maphrianate  of the East’ at   Tigrit  (Tagrit).  
  In AD 629, Patriarch of Antioch and all the East elevated  St. Marutha (Marooso) as the first MAPHRIYONO OF THE EAST for the rejuvenated  Syrian Orthodox (Jacobite) Church in Persia.  Later  the  centre  of the Maphrianate was shifted to St. Mathew’s Dayro in the city of Mosul in  Iraq and continued there till the  middle of the   19th century.   
   
Catholicate in Malankara (India)
               In 1860 the office of   Maphrianate  was abolished as per the decision of the Syrian Orthodox Church Synod held at  Deyrul' al Zafran Monastery (Kurkkumo Dayro) under Patriarch Ignatius Ya`qub II.   The same was   re-established in India  in 1964 by  the  Universal   Synod held at Kottayam, presided by Patriarch Mor Ignatius Ya`qub III.  From  the days of the establishment of this Maphrianate in India, the Church started  to officially use the title ‘Catholicos of the East’, with his jurisdiction  limited to India  in the East.   In 2002   the office of the Maphrianate was renamed   ‘Catholicos of India’ in accordance with  its  actual jurisdiction.  Present  headquarters of  this  ancient  Catholicate  (Maphrianate) of the Syrian Orthodox Church   is at Puthencuriz, Cochin,  with Catholicos Aboon Mor Baselios Thomas I as the Chief of the Church in India. 
  In Episcopal dignity the Catholicos ranks second to the  Patriarch.  As His Holiness’s deputy, the Catholicos preside over the provincial Holy Synod.   He and all the clergy of the faithful in India  pledge loyalty to the Patriarch of Antioch, the  supreme spiritual authority of the Syriac Orthodox Church throughout the world.  In its long history there are  many instances when a Maphrian (Catholicos) was elevated to the position of the  Patriarch in the Syrian Orthodox Church.  
       The Maphryono's  (Catholicos')  from the Middle East who died in India
                  1.  St. Baselios Yeldo         (d. 1685)    [entombed at the  Marthoma Church, Kothamangalam ]
                 2. Mor  Baselios Sakralla III (d. 1764)   [entombed at the  Marth Mariam Church, Kandanad] 
        The  Catholicos' of the Indian Church
                 1. Mor Baselios Augen I     (1964-1975)
                 2. Mor Baselios Paulose II   (1975-1996)   [entombed at  the  Malecuriz St. George Dayro]
                 3.  Mor Baselios Thomas I   (2002-      )
   
                 {2}    CATHOLICATE OF MALANKARA ORTHODOX SYRIAN  CHURCH 
                                                                          (Orthodox)
                                                                   This  wing  of the Orthodox Church in Kerala, India, originated in 1912 with the  establishment of an  autonomous Maphrianate/Catholicate  for the  section separated from  the  ancient Jacobite Syrian  Orthodox Christian  Community of  Malabar.  The Chief of this Church  since then  assumed the  title ‘Catholicos of the East’.  In 1934, this independent group got organised  itself under the banner ‘Malankara Orthodox Syrian Church’ with headquarters in  the town of Kottayam in southern Kerala.  Though in 1964 the group  reunited with the Universal Syrian Orthodox Church following the consecration of a  Catholicos by the Patriarch of Antioch and all the East, they once again  separated from the Holy Church in mid-1970's.  The  present Catholicos of the Church is Mar Baselios Marthoma Didymos I.
    
    
     {3}    CATHOLICATE  (PATRIARCHATE) OF THE ASSYRIAN CHURCH OF EAST 
                 (Nestorian)
                                                                                                                                                                                                                                                                   
Nestorian Church which is also called the 'Church of the  East' and more recently the 'Assyrian  Church', is one of the most important sections of the ancient Christian  Congregations in Persia.  By the end of the 5th century, when the chief of the  Persian church (Catholicos of Seleucia), adopted Nestorian doctrinal teachings,  a vast majority of faithful followed him.  In 498, the section declared their  independence claiming it as an exclusive Persian Church. Since then the  Catholicos (also called 'Catholicos-Patriarch') of the Persian Church assumed the  title 'PATRIARCH of the East, sometimes known as 'Patriarch of Babylon'.    
At present  there are two  independent Patriarchates  for the Assyrian  Church of East.   It was in the middle  of the 20th century, a split happened in the Church which resulted in the  formation of two independent factions.  The dispute  was triggered off in the Church after the reigning Patriarch Mar Simon decided  to adopt the Gregorian calendar in 1964.  But the actual reason behind  the controversy was over the hereditary succession
 of  the Patriarchs that started in 1450.  The office of the Patriarch and some other  Episcopal sees had since then become hereditary within one family, usually being  passed down from uncle to nephew. Opposing this practice, a section under  a Metropolitan separated in 1968 and this led to the formation of a parallel  Catholicate/Patriarchate.  However in 1973, the age old practice of hereditic  succession came to end with the retirement of the Patriarch Mar Simon in 1973,  who had himself become the prelate at a young age of 12.  But the division that  occurred in 1964 still continues and two parallel Patriarchates are functioning  in the Church of the East.  
 
Mar Dinkha IV with his residence in Chicago USA, is the current  Patriarch of the Assyrian Church of the East; the official name of the Church is  'Apostolic Catholic  Assyrian Church of the East'.  They follow the Gregorian calendar since 1964.   This Church has about 30,000 faithful in Kerala (India). In India the  Assyrian Church is also referred to as Chaldean Syrian Church which must not be mistaken for the Church  in Roman Catholic communion).   
   
  {4}    
CATHOLICATE OF THE ANCIENT CHURCH OF  THE EAST   
              (Nestorian)  The Ancient Church of the East was formed in 1968 following certain disputes with the Assyrian Church.  Even after the split they stick to the Julian calendar whereas the other sect is now using the Gregorian calendar. The Primate of the Church is called, the 'Patriarch of the Ancient Church of the East'.  The present Patriarch is Mar Adai II, residing in Baghdad.
  
    
   
 {5}    CATHOLICATE  (PATRIARCHATE) OF THE CHALDEAN  CHURCH OF EAST                                                                                                                                                                                                                                                                   
         (Roman Catholic)                                                                                                                                                                                                                                                                   
The Chaldean  Church which is in commune with the Roman Catholic Church is a break away group  of the Nestorian Church. The Church came into existence in AD 1445 after the  then chief of the Nestorians embraced the Roman Catholic  faith. The Chief of the Church used the title ‘Patriarch of Chaldeans’ from its  inception.  Their  headquarters is in  Bagdad,  Iraq.  The present primate of the  Chaldean church is Mar Emmanuel III Delly. The official title of the Chaldean  primate is 'Patriarch of Babylon of the Chaldeans'.   
More recently, in 2005, the Malankara Syrian Catholic  Church of India which separated from the Malankara Orthodox Church to join the  Roman Catholic Communion in 1930’s has also created a Catholicate. The first  Catholicos who adopts this title is Cyril Mar Baselios, the head of the  Malankara Catholic Church and the Archbishop of Trivandrum diocese. He is the  fourth  successor to Mar Ivanios, the founder  of the Church.  It was this Mar Ivanios,  along with Mar Dionysius Wattasseril, was instrumental in the  formation of the  Malankara Orthodox Church in India towards the beginning  of the 20th century.
source: http://catholicose.org/PauloseII/Catholicate.htm