East Syrian Rite in the context of "Cosmas Indicopleustes"

Catholicisation (American English: Catholicization) refers mainly to the conversion of adherents of other religions into Catholicism, and the system of expanding Catholic influence in politics. Catholicisation was a policy of the Holy See through the Papal States, Holy Roman Empire, Habsburg monarchy, etc. Sometimes this process is referred to as re-Catholicization although in many cases Catholicized people had never been Catholics before.

The term is also used for the communion of Eastern Christian churches into the Catholic Church; the Eastern Catholic Churches that follow the Byzantine, Alexandrian, Armenian, East Syrian, and West Syrian Rites, as opposed to the Latin Church.

The Assyrian Pentecostal Church (Syriac: ܥܕܬܐ ܕܐܚܘܢܘ̈ܬܐ ܦܢܛܩܘܣܛܝ̈ܐ ܐܬܘܪ̈ܝܐ, ‘Ittā d-Akhonāwāthā Pēnṭēqosṭāyē Ātūrāyē; Persian: کلیسای پنطیکاستی آشوری), is a Reformed Eastern Christian denomination that began in ethnically Assyrian villages across the Urmia region in northwestern Iran, spreading to the Assyrians living in the adjacent cities, and from there to indigenous Assyrian communities in the Assyrian Homeland, northern Iraq, southeastern Turkey and northeastern Syria.

The indigenous Assyrian people of ancient Assyria and Upper Mesopotamia had adopted Christianity in the 1st century AD, founding the Church of the East in Assyria and Osroene (see also: Assyria, Assyrian people and Assyrian continuity). Those who converted to the Pentecostal Church (as well as the Assyrian Evangelical Church) in the 20th century were initially all members of the Assyrian Church of the East or its later 18th century AD offshoot, the Chaldean Catholic Church, whilst others had been members of the Syriac Orthodox Church or Ancient Church of the East (a 20th-century offshoot of the Assyrian Church). The vast majority of modern-day ethnic Assyrians remain adherents of these ancient indigenous Eastern Rite churches.