[13] He was thus consecrated as patriarch of Antioch, upon which he assumed the name Ignatius and made his residence at Amida (modern Diyarbakır), but also administered the dioceses of Edessa and Damascus.
[15] In 1562, Niʿmatallah underwent a pilgrimage to Jerusalem with his brother Thomas, and whilst en route they visited the monastery of Saint Moses the Abyssinian near Al-Nabek in Syria.
[16] Niʿmatallah maintained contact with the papacy in subsequent years and sent messengers to Pope Pius IV in 1562–1565, but this was met by demands for the patriarch to make an explicit declaration of faith.
[6][nb 3] In a letter dated 28 February 1565, Pope Pius IV informed Niʿmatallah of the decrees of the Council of Trent and also of the appointment of Giovanni Battista Abissino as bishop of the Ethiopians in Cyprus, who was to act as intermediary between Rome and the eastern churches.
[18] He enjoyed greater success in internal affairs, as he restored unity within the church amidst the ongoing schism between the rival patriarchates of Antioch and Tur Abdin in 1572 after he had brought the latter under his authority.
[4] On the one hand, it is argued that Niʿmatallah was forced to resign as patriarch and convert to Islam on threat of death by the Ottoman authorities as a consequence of his contacts with the Roman Catholic Church.
[8] Whereas others assert that, whilst at Amida, Niʿmatallah had gained the favour of the city's governor, and was appointed as his private physician, ostensibly on account of his expertise in Islamic medicine.
[9] As a result, on 10 March 1576,[4] the governor placed his own turban atop Niʿmatallah's head, and announced that this act signified his conversion to Islam, to the delight of his Muslim courtiers.
In order to save himself from the Muslims' wrath, Niʿmatallah opted not to deny the governor's announcement of his conversion,[9] but in doing so traded enemies as he then became the object of his former co-religionists' fury.
[20] Fearing for his life, Niʿmatallah abdicated on 28 March 1576,[21] arranged for his brother David to succeed him as patriarch, and fled in secret with a large collection of Arabic manuscripts in his possession to a monastery near Sivas.
[4][20] Niʿmatallah thus entered into exile with his companions,[nb 4] fleeing to Venice, likely via Cyprus or Rhodes, during which he noted in an elementary mathematical text:[24][25] With the aid of the inspiration from the Mighty Lord we were able to solve these problems on Sunday, after twenty days of October of the Greek year 1888 (1576 AD) have passed, when I the lost soul, by the name of Patriarch Ni‘meh, was on the ship tossed by the waves of the sea on my way to Venice.Niʿmatallah's arrival at Venice is placed in October or November 1576.
[23] They were forced to remain at Venice for eleven months due to plague until their eventual departure on 3 December 1577, prior to which Niʿmatallah received a letter of recommendation from Giovanni Grimani, patriarch of Aquileia, dated 7 November 1577, addressed to Cardinal Gugliemo Sirleto.
[33] As protector of the College of the Neophytes, Santorio was concerned with the relationship between the papacy and the eastern churches, and after having deemed Niʿmatallah suitable, arranged financial support and lodgings for him.
[33] Leonard Abel was thus appointed titular bishop of Sidon on 19 August 1582 and nuncio in Syriae, Mesopotamiae, Assiriae, et Aegypti ac aliis Orientibus regionibus on 30 October 1582.
[7] Negotiations went poorly as the delegate responded with outrage to the Catholic condemnation of Pope Dioscorus I of Alexandria, the suggestion of the adoption of the Gregorian calendar was rejected, and the meeting was ended prematurely after rumours spread that Abel had brought weapons and funds to start an insurrection.
[44] Niʿmatallah signed the commission's final report alongside his colleagues on 14 September 1580 in Syriac and Arabic with a Latin translation of his signature provided by Leonard Abel.
[47] The Medici Press was founded with the intention of printing biblical texts in Arabic and other languages for the purpose of the promotion of Catholicism amongst Muslims and eastern Christians.
[9] Niʿmatallah's treatise in response to the Compendium novae rationis restituendi Kalendarium of 1577 was written in Garshuni in a small book (210x150mm, 55 folios) and consisted of twenty-two sections in which he extolled his criticism of the proposed reforms, followed by calendric tables and a perpetual calendar (MS Orientali 301).
[60][61] His argument for the method by which the date of Easter should be calculated made use of citations of the First Council of Nicaea, Eusebius of Caesarea, and Bar Hebraeus' Ascent of the Mind.