=== Zaman Partia dan Sasani ===
Umat Kristen sudah membentuk paguyuban-paguyuban di [[Mesopotamia]] seawal-awalnya pada abad pertama Masehi, zaman [[Kemaharajaan Partia]]. Pada tahun 266, Mesopotamia dianeksasi [[Kekaisaran Sasaniyah|Kemaharajaan wangsa Sasani]] (dijadikan daerah [[Asōristān]]). Saat itu sudah ada paguyuban-paguyuban Kristen yang cukup besar di daerah [[Mesopotamia Hulu]], [[Elam]], dan [[Provinsi Fars|Fars]].{{sfn|Baum|Winkler|2003|p=1}} Gereja di Timur mengaku sebagai hasil pewartaan Injil yang dilakukan [[Tadeus dari Edessa|Adai]], [[Santo Mari|Mari]], dan [[Tomas|Rasul Tomas]]. Tatanan maupun kepemimpinannya baru disempurnakan pada tahun 315, ketika [[Papa (uskup)|Papa bar Aggai]] (310–329), Uskup [[Seleukia]]-[[Ktesifon]], memaksa semua keuskupan lain di Mesopotamia dan Persia untuk mengakui takhta keuskupannya sebagai pusat kepemimpinan gerejawi. Keuskupan-keuskupan tersebut dipersatukan di bawah kepemimpinan Katolikos Seleukia-Ktesifon. Papa bar Aggai menggelari dirinya [[Katolikos]] (pemimpin umum).<ref>[[Ilaria Ramelli]], “Papa bar Aggai”, dalam ''Encyclopedia of Ancient Christianity'', edisi ke-2, 3 jld., penyunting: Angelo Di Berardino (Downers Grove, IL: InterVarsity Press, 2014), 3:47.</ref> JabatanPada initahun diberi410, gelar tambahanini pada tahun 410diperpanjang sehinggalagi menjadi "[[Daftar Batrik Gereja di Timur|Katolikos dan Batrik di Timur]]".{{sfn|Fiey|1967|p=3–22}}{{sfn|Roberson|1999|p=15}}<!--
TheseJumlah earlyanggota Christianpaguyuban-paguyuban communitiesKristen indi Mesopotamia, Elam, anddan Fars weremembengkak reinforcedpada inabad theke-4 4thdan andke-5 5thsaat centuriesterjadi bydeportasi largebesar-scalebesaran deportations ofumat ChristiansKristen fromdari thewilayah easterntimur [[RomanKekaisaran EmpireRomawi]].{{sfn|Daniel|Mahdi|2006|p=61}} HoweverMeskipun demikian, theGereja PersianPersia Churchdihadapkan facedkepada severalberbagai severe persecutionsaniaya, notablyterutama duringaniaya thepada reignmasa ofpemerintahan Syahansyah [[ShapurSyapur II]] (339–79), fromyang thedilakukan warga mayoritas [[ZoroastrianismZoroastrianisme|ZoroastrianMazdayasna]] majorityyang whomenuding accusedumat itKristen ofsebagai Romanantek-antek leaningsRomawi.{{sfn|Foster|1939|p=26-27}} ShapurSyapur II attemptedberusaha tomembubarkan dismantlestruktur theketatalaksanaan catholicate'sGereja structuredi andnegaranya, putbahkan tomenghukum deathmati somesejumlah ofrohaniwan, thetermasuk clergy including the catholicoiKatolikos [[Shemon Bar Sabbae|Simeon bar SabbaSaba'e]] (pada tahun 341),{{sfn|Burgess|Mercier|1999|p=9-66}} Katolikos [[ShahdostSyahdost]] (pada tahun 342), anddan Katolikos [[Barba'shminsymin]] (pada tahun 346).<ref>Donald Attwater & Catherine Rachel John, ''The Penguin Dictionary of Saints'', 3rdedisi ednke-3. (New York: Penguin Books, 1993), 116, 245.</ref> Afterward,Sesudah theKatolikos officeBarba'symin ofdihukum Catholicosmati, layjabatan vacantkatolikos nearlylowong hampir 20 yearstahun lamanya (346–363).{{sfn|Tajadod|1993|p=110–133}} InPada tahun 363, underberdasarkan the terms of asyarat-syarat peacekesepakatan treatydamai, Nisibis wasdiserahkan cededkepada tobangsa the Persians,Persia. causingAkibatnya [[EphremEfrem theorang SyrianSuriah]], accompaniedbersama bysejumlah apengajar number of teachers, to leave themeninggalkan [[School ofPerguruan Nisibis]] fordan hijrah ke [[EdessaEdesa]] stillyang masih termasuk wilayah inkedaulatan RomanKekaisaran territoryRomawi.{{sfn|Labourt|1909}} TheGereja churchdi grewTimur considerablycukup duringberkembang thepada Sasanianzaman periodkulawangsa Sasani,<ref name=Britannica/> buttetapi theaniaya pressureterhadap ofumat persecutionKristen ledmendorong theKatolikos Catholicos DadishoDadisyo I inuntuk 424menggelar toSinode conveneMarkabta thedi SynodSeleukia oftahun Markabta424 atdan Seleuciamemaklumkan andkemandirian declareGereja thedi CatholicateTimur independent fromdari "the westernBapa-Bapa FathersBarat".{{sfn|Jugie|1935|p=5–25}}
MeanwhileSementara itu, indi theKekaisaran Roman EmpireRomawi, the [[NestorianSkisma SchismNestorian]] hadmendorong ledbanyak many ofpendukung Nestorius' supportersuntuk tohijrah relocateke towilayah thekedaulatan Sasaniankulawangsa EmpireSasani, mainlykhususnya aroundke thedaerah theologicalsekitar [[School ofPerguruan Nisibis]]. TheGereja Persiandi ChurchTimur increasinglykian alignedlama itselfkian withakrab thedengan Dyophisiteskaum Diofisit, abahkan measurekedekatan encouragedsemacam byini thedidukung Zoroastrianpara rulingpenguasa classyang beragama Mazdayasna. TheSepanjang churchbeberapa dasawarsa selanjutnya, becamedoktrin increasinglyGereja Dyophisitedi inTimur doctrinekian overcondong theke nextpaham decadesDiofisitisme, furtheringsehingga thejurang dividedi betweenantara RomanKekristenan anddi PersianKekaisaran Christianity.Romawi Indan 484Kekristenan thedi MetropolitanPersia ofkian melebar. Pada tahun 484, Metropolit Nisibis, [[Barsauma]], convened themenggelar [[Synod ofSinode BethBet Lapat]], wheredan hesecara publiclyterbuka acceptedmenerima Nestorius'guru mentorNestorius, [[TheodoreTeodorus ofdari Mopsuestia]], assebagai apemangku spiritualkewenangan authorityrohani.{{sfn|Baum|Winkler|2003|p=28-29}} InPada tahun 489, when theketika [[SchoolPerguruan of EdessaEdesa]] indi [[Mesopotamia (Romanprovinsi provinceRomawi)|Mesopotamia]] was closed by Byzantine Emperorditutup [[Zeno (emperorkaisar)|Kaisar Zeno]] forlantaran itsmengajarkan Nestorian teachingsNestorianisme, theperguruan schooltersebut relocatedberpindah tolokasi itske originalNisibis, hometempat of Nisibisasalnya, becomingsehingga againsekali thelagi menjadi [[School ofPerguruan Nisibis]],. leadingSituasi toini amendorong wavepara ofpenganut NestorianNestorianisme immigration intoberbondong-bondong thebermigrasi Sasanianke EmpirePersia.{{sfn|Reinink|1995|p=77-89}}{{sfn|Brock|2006|p=73}} TheBatrik Patriarchdi of the EastTimur, [[Mar Babai I]] (497–502), reiteratedmenegaskan andkembali expandedpenghargaan uponpara hispendahulunya predecessors'kepada esteemTeodorus fordari TheodoreMopsuestia, solidifyingsehingga kian mengukuhkan penerimaan Gereja thedi church'sTimur adoptionterhadap ofdoktrin DyophisitismDiofisitisme.<ref name=Britannica/>
[[File:Church of Saint John the Arab.jpg|thumb|225px|AGereja 6thSanto centuryYohanes NestorianOrang churchArab, St.gereja JohnNestorian thedari Arab,abad inke-6 thedi [[Assyrian peopleAndak|AssyrianGeramon]], villagesebuah ofdesa yang dihuni masyarakat [[Andacbangsa Asiria|GeramonAsyur]].]]
NowSesudah firmlykuat establishedberakar indi theKemaharajaan PersianPersia Empire,serta withmendirikan centrespusat-pusat indi Nisibis, [[CtesiphonKtesifon]], anddan [[GundeshapurGundesyapur]], andmaupun severalbeberapa [[metropolitantakhta seemetropolia]]s, theGereja Churchdi ofTimur themulai Eastmelebarkan begansayapnya toke branchluar outwilayah beyondPersia. theMeskipun Sasaniandemikian, Empire.pada abad Howeverke-6, throughGereja thedi 6thTimur centuryberulang thekali churchdirongrong waspertikaian frequentlyinternal besetmaupun withaniaya internaldari strifeumat andMazdayasna.<!-- persecutionPertikaian frominternal theberbuntut Zoroastrians.skisma Theyang infightingbermula ledpada totahun a521 schism,dan whichbaru lastedberakhir fromsesudah 521masalahpermasalahannya diselesaikan until around 539, when the issues were resolved. However, immediately afterward Byzantine-Persian conflict led to a renewed persecution of the church by the Sasanian emperor [[Khosrau I]]; this ended in 545. The church survived these trials under the guidance of Patriarch [[Aba I]], who had converted to Christianity from [[Zoroastrianism]].<ref name=Britannica/>
By the end of the 5th century and the middle of the 6th, the area occupied by the Church of the East included "all the countries to the east and those immediately to the west of the Euphrates", including the Sasanian Empire, the [[Arabian Peninsula]], [[Socotra]], [[Mesopotamia]], [[Medes|Media]], [[Bactria]], [[Hyrcania]], and [[India]]; and possibly also to places called Calliana, Male, and Sielediva (Ceylon).{{sfn|Stewart|1928|p=13-14}} Beneath the Patriarch in the hierarchy were nine [[metropolitan bishop|metropolitans]], and clergy were recorded among the [[Huns]], in [[Persarmenia]], Media, and the island of [[Dioscoris]] in the [[Indian Ocean]].{{sfn|Stewart|1928|p=14}}
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