André de Longjumeau was a 13th century Dominican

Dominican Order

The Order of Preachers , after the 15th century more commonly known as the Dominican Order or Dominicans, is a Catholic religious order founded by Saint Dominic and approved by Pope Honorius III on 22 December 1216 in France...

 missionary and diplomat and one of the most active Occidental diplomats in the East in the 13th century. He led two embassies to the Mongols

Mongol Empire

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

: the first carried letters from Pope Innocent IV

Pope Innocent IV

Pope Innocent IV , born Sinibaldo Fieschi, was pope from June 25, 1243 until his death in 1254.-Early life:...

 and the second bore gifts and letters from Louis IX of France

Louis IX of France

Louis IX , commonly Saint Louis, was King of France from 1226 until his death. He was also styled Louis II, Count of Artois from 1226 to 1237. Born at Poissy, near Paris, he was an eighth-generation descendant of Hugh Capet, and thus a member of the House of Capet, and the son of Louis VIII and...

 to Güyük Khan

Güyük Khan

Güyük was the third Great Khan of the Mongol Empire. As the eldest son of Ögedei Khan and a grandson of Genghis Khan, he reigned from 1246 to 1248...

. Well acquainted with the Middle-East, he spoke Arabic

Arabic language

Arabic is a name applied to the descendants of the Classical Arabic language of the 6th century AD, used most prominently in the Quran, the Islamic Holy Book...

 and "Chaldean

Chaldean Neo-Aramaic

Chaldean Neo-Aramaic is a Northeastern Neo-Aramaic dialect. Chaldean Neo-Aramaic is spoken on the plain of Mosul in northern Iraq, as well as by the Chaldean communities worldwide. Most speakers are Chaldean Catholics....

" (thought to be either Syriac

Syriac language

Syriac is a dialect of Middle Aramaic that was once spoken across much of the Fertile Crescent. Having first appeared as a script in the 1st century AD after being spoken as an unwritten language for five centuries, Classical Syriac became a major literary language throughout the Middle East from...

 or Persian

Persian language

Persian is an Iranian language within the Indo-Iranian branch of the Indo-European languages. It is primarily spoken in Iran, Afghanistan, Tajikistan and countries which historically came under Persian influence...

).
Andrew's first mission to the East was when he was asked by the French king Louis IX

Louis IX of France

Louis IX , commonly Saint Louis, was King of France from 1226 until his death. He was also styled Louis II, Count of Artois from 1226 to 1237. Born at Poissy, near Paris, he was an eighth-generation descendant of Hugh Capet, and thus a member of the House of Capet, and the son of Louis VIII and...

 to go and fetch the Crown of Thorns

Crown of Thorns

In Christianity, the Crown of Thorns, one of the instruments of the Passion, was woven of thorn branches and placed on Jesus Christ before his crucifixion...

 which had been sold to him by the Latin king of Constantinople

Constantinople

Constantinople was the capital of the Roman, Eastern Roman, Byzantine, Latin, and Ottoman Empires. Throughout most of the Middle Ages, Constantinople was Europe's largest and wealthiest city.-Names:...

 Baldwin II

Baldwin II of Constantinople

Baldwin II of Courtenay was the last emperor of the Latin Empire of Constantinople.He was a younger son of Yolanda of Flanders, sister of the first two emperors, Baldwin I and Henry of Flanders...

 in 1238, who was anxious to obtain support for his tottering empire.