The country of Chaldea was an ancient land in southern Babylonia, on the Persian Gulf near the delta of the Tigris and Euphrates rivers. In biblical times the name was applied to all of Babylonia. As far as can be traced, the Chaldeans themselves descend from Shem's son, Arphaxad, who is also an ancestor of Abraham and Israel.
Chaldeans are associated with Babylon and the city of Ur because they settled near Babylon and in Shinar. In fact, the most powerful Babylonian dynasty (Neo-Babylonia, c. 625-539 BC) was Chaldean, as was its most powerful and most famous king, Nebuchadnezzar (reigned c. 604-561 BC, see II Kings 24:1—25:21; II Chronicles 36:5-21; Jeremiah 39:1-14; Daniel 1:1—4:37). However, some Chaldeans settled farther north, around Lake Van—about halfway between the Mediterranean Sea and the Caspian Sea. There they came to be called "Chaldians" and, more often, the people of Van. (Haran, the ancestor of Lot, Abraham's nephew, also settled in northern Mesopotamia, south of Lake Van.)
History records that some of the "Chaldians" were driven northward out of the Near East by the Assyrians and Medes prior to 610 BC (An Encyclopaedia of World History, by William L. Langer, p. 38). From the shores of the Black Sea, they turned to southeastern Europe, then after a time headed west into the Roman Empire. They settled in northern Italy, southeastern France, and parts of Spain and northern Africa.
The ancient Chaldeans of Babylonia were also sent into exile to Syria in the Greek period of rule over Babylon. Many peoples calling themselves Chaldeans still live in Syria and the surrounding regions. During the time of the Roman Empire, Latin Romans often bought these people as slaves for their European villas, and afterward, their descendants were freed and settled nearby. Thus, wherever the Chaldeans are mentioned in Bible prophecy, the reference is primarily to these people in central and southwestern Europe.