Chaldea corresponds to the geographical territory situated within the south-eastern marshlands and coastal plains of southern Babylonia along the Euphrates and Tigris rivers.

From the beginning of the second millennium BCE, an influx of semi-nomadic clans infiltrated southern Babylonia in waves. The Chaldeans controlled much of southern Babylonia's trade routes due to the territory's adjacency to the Persian Gulf.

In antiquity, the Chaldeans were also the driving force behind the advancement of Babylonian astronomy and science. Chaldean philosophers sophisticated the already established observations and devised complex theories to describe the cosmological phenomena.

Related: Brief History of Assyrians
Related: Assyrians: Frequently Asked Questions

According to the table of nations, the Biblical Chaldeans were descended from Arpachshad, grandson of Noah.

During the advent of Christendom, the earliest manifestation of the Chaldeans is attested in the first century AD manuscripts entitled 'The Teaching of the Twelve Apostles.' The text constitutes the earliest principles concerning Christian ethics, rituals, church organisation, and baptism.

The Apostles further appointed: Whosoever resorts to magicians and soothsayers and Chaldeans, and puts confidence in fates and nativities, which they hold fast who know not God,- let him also, as a man that knows not God, be dismissed from the ministry, and not minister again. - Teaching of the Twelve Apostles (c. 65 AD)

The Chaldeans profess to be acquainted with the horoscope. - Hippolytus of Rome (c. 200 AD)

Early Syriac narratives for instance that of the 'Doctrines of Addai' also indicate the Chaldeans neither embraced the Holy Gospels nor the newly founded religion 'Christianity.' Converts to Christendom were encouraged not to associate with the Chaldeans.

The term 'Chaldean' was stigmatised by the early Church fathers and employed in a derogatory connotation.

In c. 800 AD, Abbasid Caliph al-Ma'mun came into contact with the Chaldeans in the ancient city of Harran. The caliph observed that the Chaldeans practised a form of astrolatry and were not recognised as a “dhimmi.”

The term "dhimmi” refers to non-Muslim citizens of an Islamic state. The word literally means "protected person." Followers of monotheistic religions enjoyed some level of privileges under Islamic law.

The Caliph commanded the Chaldeans to either embrace one of the religions mentioned in the Koran or face death. A local tribal sheikh encouraged the Chaldeans to identify as Sabeans. The Chaldeans thus renounced their identity and embraced the Sabean nomenclature.

Early Islamic and Judaic scholarly narratives corroborate this historical event.

The Chaldeans are also called Sabeans, the name Sabeans was applied to them at the time of al-Ma'mun. - al-Khwarizmi (c. 839 AD)

Then he, the sheikh said to them when al-Ma'mun returns from his journey, say to him, 'we are Sabeans,' for this is the name of a religion which Allah, may his name be exalted, mentioned in the Koran. Profess it and you will be saved by it. - Ibn al-Nadim (c. 900 AD)

What is left of the Chaldeans is now in the two cities Harran and Roha, and that they in the time of al-Ma'mun gave up the name Chaldeans and took the name Sabeans. - Hamzah al-Issfahani (c. 900 AD)

It is well known that the Patriarch Abraham was brought up in the religion and the opinion of the Sabeans, that there is no divine being except the stars. - Musa Ibn Maymun (c. 1200 AD)

During the early Middle Ages, East Syriac Christians inhabited the northern territory of Cyprus. This community adhered to the Church of the East and were also denominationally known as Nestorians. The Roman Catholic Church viewed the Nestorians as heretics and exhausted every effort in converting them to Catholicism.

In 1445 AD, the Council of Florence presided by Pope Eugene IV succeeded in welcoming the community into Catholicism. Furthermore, the Papacy constructed a distinct confessional body and bestowed upon them the unmeaning title of 'Chaldeans.'

Why Chaldean?

The sacred liturgies practised by this community was conducted in the East Syriac dialect which the Papacy romanticised and synonymously regarded as Chaldaic- with reference to the Biblical Book of Daniel.

According to Medieval scholars, the Ethiopian (Abyssinian) faction denominationally identified its community as 'Chaldean' indicating that the term was neither exclusive to the East Syriac Christian converts, nor was it employed to designate an ethno-political identity.

The Ethiopians call themselves Chaldeans. - Joseph Justus Scaliger (c. 1540 AD)

Six centuries since it was renounced, the Chaldean identity was thus revived by the Roman Catholic Church.

In 1552 AD, a power struggle broke out within the Church of the East which provoked distrust amongst various monks toward their anointed Patriarch.

Yohanan Sulaqa, a schismatic monk failed in legitimising his candidacy to topple the Patriarchate thus journeyed to Rome and presented his confession of faith before Pope Julius III. The Papacy consecrated Sulaqa 'Patriarch of the Eastern Assyrians' presiding over the Catholic 'Church of Mosul in Assyria.'

A rival Patriarchate was now formed.

In efforts of reinforcing the union, the Papacy came to denominate the Catholic portion 'Chaldeans' in conformity with the precedent converts in Cyprus a century earlier. In c. 1844 AD, the so-called Chaldean Patriarch was encouraged by the Holy See to journey to Constantinople in order of attaining a Ottoman mandate recognising the Chaldean Catholics as a distinct community to that of the Nestorians.

The ambitious views of the Roman pontiffs sowed the pestilential seeds of animosity and discord among all Eastern Churches; and the Nestorian Christians, who are also known by the denomination of Chaldeans, felt early the effects of their imperious councils. - Johann Lorenz Mosheim (c. 1726 AD)

They distinguish themselves by the name of Chaldeans for they detest and abhor the denomination, or distinction of Nestorians. - Cornelius De Bruyn (c. 1736 AD)

The Christians who are born in the towns of Mosul, and of Mardin, do not speak a word of Chaldaic, at least it is not their mother tongue. - Carsten Niebuhr (c. 1797 AD)

The present Chaldean Christians are of a recent origin. The sect was as new as the office, and was created for it. Converts to the Papacy from the Nestorian and Jacobite Churches were unified in one body, and dignified by the name of the Chaldean Church... In fact, all the Nestorian Church books are used by the Chaldeans. The priest seemed to think, that, in conformity with the name of his Church, its books must in ancient times have been written in the Chaldean character, but confessed at present it posses no such books, and only uses the Nestorian character (Syriac). - Rev Eli Smith (c. 1833 AD)

The so-called "Chaldeans" of Mesopotamia recieved that title, as you know, from the Pope, on their becoming Catholics. - Edward Robinson (1841 AD)

The Pope bestowed upon them, the venerable, but unmeaning title of Chaldeans, which they now claim; Although they were and are truly nothing more than Papal Nestorians, or Nestorian Catholics. - North American Review (c. 1843 AD)

The community styling themselves "Chaldeans," had not been recognised by the Ottoman Porte. This was the first recognition by the Ottoman Porte of the new community. - George Percy Badger (c. 1844 AD)

To the title which the Pope has given to them of "Chaldean Christians," they have no exclusive claim, not such a strong claim, indeed. - John Wilson (1846 AD)

Chaldeans. A modern sect of Christians in the East, in obedience to the see of Rome. - Walter Farquhar Hook (1859 AD)

At the schism on account of Nestorius, the Assyrians, under the generic name of the Chaldean Church, mostly separated from the Orthodox Greeks, and, being under the rule of the Persians, were protected against persecution. - Henry John Van-Lennep (1875 AD)

Another fact connected with the nationality of the Chaldeans which goes far to show they are as much entitled to Assyrian descent as any other community which boasts of ancient origins. - Hormuzd Rassam (c. 1898 AD)

Strictly, the name of Chaldeans is no longer correct. - The Catholic Encyclopedia, vol. 3 (1908 AD)

It may not be out of place, therefore, to point out that there were exceedingly few Roman Catholic Assyrians or "Chaldeans" as they are generally termed when they embrace Rome, amongst the refugees at Baqubah. The very large majority of the Roman Catholic Assyrians in the Mosul vilayet did not join the mountaineers and fight against the Turks in consequence were permitted by the Turks to continue to dwell practically unmolested in their homes about Mosul. - Herbert Henry Austin (1920 AD)

The modern usage of the Chaldean identity is challenged by conflicting historical narratives.

The Sabeans are the Chaldeans. - Joseph Justus Scaliger (c. 1540 AD)

The Chaldeans, that lived towards the foot of the river Euphrates, were called Sabeans by the Arabians and Jews. - George Mackenzie (c. 1711 AD)

The Chaldee language of the Sabeans. - William Tooke (c. 1769 AD)

Sabeans, or Christians of St. John, as they are vulgarly called, who lived near what was considered to be ancient Chaldea, and who are generally supposed to be descendants of the old Babylonians and Chaldeans. - John Philip Newman (c. 1826 AD)

Whenever the term "Chaldean" occurs in the Nestorian rituals, which it does only in two instances, it is not used to designate a Christian community, but the ancient sect, who have been called also Sabeans. - George Percy Badger (c. 1844 AD)

The sect variouslty known by the names of Sabeans, presents the most curious combination of wholly diverse creeds that can be conceived. As the descendants of the ancient Semitic population of Chaldea, and the inheritors of the Babylonian language. - Stanley Lane-Poole (c. 1883 AD)

The Kasdim, the Chaldeans and the Sabeans, are only different names successively given to the same people. In the time of the Bible they were called Kasdim; in the age of the Talmud they were the Chaldeans, and later they recieved the name of the Sabeans. - Michael Friedlander (c. 1890 AD)

Presently, the Sabeans of the south-eastern marshlands and coastal plains of southern Iraq identify as 'Mandaean.' The term is derived from the ancient Babylonian 'Mandetu' meaning 'the knowledgeable.' The Mandaean Book of the Zodiacs bears rich testimony to various astrological and ancient Chaldean doctrines.

Editor's Note: The modern Chaldeans, who are Roman Catholic Assyrians, are not related to the ancient Chaldeans of South Iraq.