A friend of mine recently met some Chaldeans in Michigan, and as I am his go-to guy for all matters Middle Eastern and Christian, he asked me who they were. Here is my response, lightly edited for broader publication:
The subject of Chaldean ethnicity is rather complicated. Basically “Chaldeans” are Catholic “Assyrians,” as these two terms get used in modern Iraq. The connection with the “Assyrians” of the Old Testament (much less the astrologers of Daniel 2) is debatable.
A more detailed answer must be aware of the fact that Christianity in Iraq has almost disappeared as a result of a very difficult past century. Widespread massacres in 1915 (better known in the West as the Armenian Genocide, although Armenians were not the only targets) killed large numbers and drove them south into the central Iraqi plain. At the end of World War I, while the victorious Western powers were meeting in Paris, British officers in Iraq encouraged an Assyrian leader named Agha Petros to try to capture a territory for an Assyrian “homeland” and present the victors with a fait accompli; the attempt was disastrous. The British Mandate government which subsequently ruled Iraq frequently used the Assyrian Christians as a paramilitary force, which made them deeply unpopular with other groups in the area. After the British pulled out in 1932, the Simele massacres of 1933 further reduced Assyrian numbers and solidified Iraqi national sentiment against the Assyrians. Many Assyrians emigrated from Iraq in this period. Those who remained stabilized as a small minority within Iraq, and pressures to abandon the Assyrian neo-Aramaic language in favor of either Arabic or Kurdish have been intermittently very high. Saddam Hussein was seen by a few (notably Jean-Maurice Fiey before 1973) as more friendly to Christians (his foreign minister Tariq Aziz is a Chaldean Catholic), though his Arab Nationalist Ba’ath party also discouraged the use of Assyrian neo-Aramaic in favor of Arabization. Assyrians today speak not only of the genocide of 1915, but also of a cultural genocide. So one must be careful how one addresses the history of an endangered minority. Nevertheless, history cannot be written to serve present pain.
Most Assyrians emphasize that their ethnic identity has not changed since before the rise of Islam. So I’ll give you three perspectives: the “traditional” Assyrian view (as forcefully expressed by various Assyrians I have met), the widely held scholarly view, and my compromise.
The “traditional” Assyrian view
Don’t be misled by the label “traditional”; one Orthodox priest used to say that unchanging tradition is whatever your grandmother did. It need not be older than a century. But this view says that the ancient Assyrians who ruled much of the Near East from their capital at Nineveh never died out. Instead they were conquered by the Babylonians (in 612 BCE), the Achaemenid Persians (in the late 500s BCE), Alexander the Great (shortly before 300 BCE), the Parthians (in the 220s BCE), the Romans (briefly in the 110s CE), the Sasanian Persians (in the 230s CE), the Muslim Arabs (in the 630s and 640s), the Mongols (in the mid-13th C), and the Ottomans (in the 1530s). In the meantime, the apostle Thomas had sent his disciple Addai to Edessa (modern Urfa in SE Turkey), and Addai in turn sent his disciple Mari to Seleucia and Ctesiphon, the capitals of the Persian Empire. They converted the Assyrians among various other peoples, and although they used Syriac in the churches, they continued to speak Assyrian neo-Aramaic. Assyrians practiced Christianity in large numbers and flourished in the plain around Mosul (founded across the Tigris river from ancient Nineveh), until at the end of the 14th C Timur Lenk (“Tamerlane”) conquered the region and slaughtered them, and many of them retreated to the mountains to the north. (In the 16th C, many of those left in the plains adopted Catholicism and became “Chaldeans.”) The “Mountain Nestorians” were the target of American and British missionary ventures in the 19th C, and during the sufferings of the twentieth century, those who could fled to the West (especially Chicago, Stockholm, and Melbourne, but also London, Detroit area, and other places). Thus they are the ancient Assyrians, who recently have suffered genocide and cultural extermination.
The “standard” scholarly view
A few scholars accept the “traditional” Assyrian view, but most do not. The skeptics point out that when the American missionaries traveled to the “Mountain Nestorians” in the 1830s and 1840s, they claimed to be the ten lost tribes of Israel! On the most common view, the term “Chaldean” was not used within this community before the 1700s, being translated from the Latin. The first use of the term “Chaldean” to refer to a contemporary community since antiquity was in 1445, when a branch of the Church of the East in Cyprus submitted to the Papacy and was called “Chaldean”. The merger didn’t last long, but in 1553 a monk from northern Iraq traveled to Rome to ask to be appointed “Patriarch of Babylon,” and he and those who followed him were termed Chaldeans in Latin. In Renaissance Europe, the main dialect of Aramaic which was studied was the one in Daniel 2 (and other biblical texts), which was termed “Chaldean” due to the fact that in the text it is the Chaldeans who first speak it to Nebuchadnezzar. So when Christians from northern Iraq showed up speaking a (rather different) dialect of Aramaic, they were labeled “Chaldeans”. The term “Assyrian,” it is claimed, was not used for a contemporary community until the English adventurer/archaeologist (Indiana Jones type) Henry Layard discovered the ruins of ancient Nineveh across from the city of Mosul. In light of 19th C European theories of racial fixedness and physiognomy, Layard and other Brits after him declared that the Christians of the area were clearly “Assyrians,” from their facial resemblance to the stone reliefs which colonial antiquities collectors were busy bringing back to the British Museum in London. In the second half of the 19th C, the term “Assyrian” was adopted by the community itself as an importation of European nationalism in order to argue for their right to political autonomy against the Ottoman Empire (just as the Greeks had done earlier). With the genocide in the early 20th C and the 1933 massacres, ethnic identity assumed primacy over religious identity within this community, especially as they continued (whether still in Iraq or now in the West) to lobby for political autonomy using European terms. Thus there is no continuity between the ancient Assyrians and the modern Assyrians.
There are various mediating positions which scholars adopt between the extreme view just summarized and the “traditional” view. A few details: the term “Assyrian” was known and used before 1840, in various centuries. For example, the 2nd C Christian author Tatian identified himself in Greek as “Assyrios.” The Armenians used “Asoristan” (the “land of the Assyrians”) straight through the medieval period, and also (though less commonly, perhaps) used the group name “Asorik’.” The Syriac terms “Athor” (a place) and “Athoraya” (a person from that place) were very rarely used from the fifteenth to the eighteenth century. Additional citations can be found on the Wikipedia page “Assyrian Continuity“.
The difficulty is that proponents of Assyrian continuity typically fail to ask the question what “Assyrian” means in different contexts, but assume its meaning is unchanging. What Tatian meant, I am not sure, but probably appealed to a Mesopotamian birth (and not all Mesopotamians are or were “Assyrians” in the modern sense). The eleventh-century Greek historian Michael Attaleiates termed one person an “Assyrios” on account of his having been born in Antioch in Syria, not in Mesopotamia at all. The Armenian “Asuristan” is clearly a designation for Iraqi Mesopotamia as distinct from “Mijaget” (“Mesopotamia”), which was used for upper Mesopotamia in what is now Syria and Turkey, and “Sham” (Syria southwest of the Euphrates). The Syriac “Athor” refers to the region around Mosul in northern Iraq, and “Athoraya” refers exclusively to someone from that small region, not to any of the people in other regions (such as the mountains of Kurdistan or Hakkari, or the plain west of the Lake Urmia in NW Iran) whose descendants now call themselves “Assyrians.” So some memory of Mosul as the capital of the ancient Assyrian Empire seems to have survived.
But pre-modern Middle Easterners did not use ethnic names for enduring descent groups, as became popular in modern Europe. So “ethnic” labels such as “Assyrian” should be understood with reference to places, languages, or religious groups. (Indeed, the “ethnic” term preferred by 17th C poets who would later be called “Assyrians” was not “Athoraye” but “Suraye” – i.e. Syriac speakers.) Given the American missionaries’ reports that the “Mountain Nestorians” in the 1830s believed they were the ten lost tribes of Israel, it seems likely that leaders in the community were willing to adopt whatever “ethnic” label would be most advantageous, and one can hardly blame them in light of their subsequent sufferings. Thus it is simply false to say that there has always been a well-defined ethnic group known as the “Assyrians” to themselves and to others, who preserved the cultural identity of Sargon and Sennacherib and the ancient Assyrian Empire.
On the other hand, it is certainly true that the ancient Assyrians were not exterminated, so the modern Assyrians are probably descendants of the ancient Assyrians. But the ancient Assyrians are not known to have practiced strict endogamy, so they certainly intermarried with newcomers in the form of Israelite captives, Kurds, Persian conquerors, a small group of Greek invaders, Armenians, Arabs, and finally Turks. Just as my own “northwestern European” cocktail of ancestry is not distinctively French, English, German, or Irish, much less any specific tribe in any of these areas, so modern Assyrians can count their ancestors from many different groups. Modern Assyrian culture is probably also a continuous development from ancient Assyrian culture, but again not exclusively, as their Aramaic dialects absorbed words of Persian (in at least two waves), Arabic, Kurdish, and Turkish. So ancient Assyrian culture would be as unrecognizable to modern Assyrians as painting oneself blue is to modern Brits. In the 15th C, the Church of the East still thought of itself as a universal church, and identified several ethnic labels within its ranks.
But as Christians in the Hakkari Mountains and Iraq encountered European ideas of ethnic persistence and self-determination, they cast about for which ethnicity they could claim, and “Assyrian” seemed a sensible choice which was close to hand. The problem is that those European ideas of ethnic persistence and physiognomy are demonstrably wrong, and yet ethnic essentialism persists among Middle Eastern Christians still hoping in vain for Western world leadership to live up to Western political ideals of national autonomy and self-determination.
You can see why it’s a sensitive topic. But the short answer is that “Chaldeans” are Catholic “Assyrians.”