Isa Tarsah Kelemechi was a Syrian (probably Assyrian) Nestorian Christian scientist, and official at the Yuan court of Kublai Khan

Kublai Khan

Kublai Khan , born Kublai and also known by the temple name Shizu , was the fifth Great Khan of the Mongol Empire from 1260 to 1294 and the founder of the Yuan Dynasty in China...

's Mongol Empire

Mongol Empire

The Mongol Empire , initially named as Greater Mongol State was a great empire during the 13th and 14th centuries...

 in the 13th century.

Astrologer in China

Isa Kelemechi was named head of the "Office of Western Astronomy" established by the Mongol ruler Kubilai Khan in 1263 to study Muslim

Muslim

A Muslim, also spelled Moslem, is an adherent of Islam, a monotheistic, Abrahamic religion based on the Quran, which Muslims consider the verbatim word of God as revealed to prophet Muhammad. "Muslim" is the Arabic term for "submitter" .Muslims believe that God is one and incomparable...

 astronomical observations. Kubilai would establish a second Observatory for Islamic astronomy in 1271, directed by astronomer Jamal al-Din

Jamal ad-Din (astronomer)

Jamal ad-Din Muḥammad ibn Ṭāhir ibn Muḥammad al‐Zaydī al‐Bukhārī was a 13th-century Persian-speaking Muslim astronomer...

.

Isa Kelemechi was also instrumental in reinforcing anti-Muslim prohibitions in the Mongol realms, such as prohibiting halal

Halal

Halal is a term designating any object or an action which is permissible to use or engage in, according to Islamic law. The term is used to designate food seen as permissible according to Islamic law...

 slaughter and circumcision

Circumcision

Male circumcision is the surgical removal of some or all of the foreskin from the penis. The word "circumcision" comes from Latin and ....

, and, according to Rashid al-Din encouraged denounciation of Muslims. Isa Kelemechi also showed to Khubilai the Muslim precept of "Kill the polytheists, all of them", raising the suspicion of the Mongols towards Muslims. According to Rashid al-Din, as a result "most Muslims left Khitai".

Diplomat to Europe

Isa Kelemechi was later a member of the first mission to Europe sent by the Mongol Il-Khan ruler Arghun

Arghun

Arghun Khan aka Argon was the fourth ruler of the Mongol empire's Ilkhanate, from 1284 to 1291. He was the son of Abaqa Khan, and like his father, was a devout Buddhist...

 in 1285. He met with Pope Honorius IV

Pope Honorius IV

Pope Honorius IV , born Giacomo Savelli, was Pope for two years from 1285 to 1287. During his unremarkable pontificate he largely continued to pursue the pro-French policy of his predecessor, Pope Martin IV...

, remitting a letter from Ghazan offering to "remove" the Saracens and divide "the land of Sham, namely Egypt

Egypt

Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...

" with the Franks. The message, written in imperfect Latin, said:
The 1285 embassy would be followed in 1287 by that of Rabban bar Sauma

Rabban Bar Sauma

Rabban Bar Sauma , also known as Rabban Ṣawma or Rabban Çauma, , was a Turkic/Mongol monk turned diplomat of the Nestorian Christian faith. He is known for embarking on a pilgrimage from Mongol-controlled China to Jerusalem with one of his students, Rabban Markos...

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