Chaldea was described as a region within Mesopotamia that resided near the Persian Gulf. The modern day location for Chaldea is probably Iraq and possibly a portion of Iran. Neighboring the Chaldeans were the Babylonians to the northwest and the Elamites to the northeast.
As stated in Genesis 11:28-31 and 15:7 as well as Nehemiah 9:7, the primary Chaldean town was Ur, where Abram (Abraham) came from and where his brother Haran was buried. In Stephen's speech to the Sanhedrin before he was stoned as a martyr, he spoke of Abraham in Acts 7:4.
Chaldeans were involved in raids against Job in Job 1:17.
The Chaldeans and Elamites helped the Babylonians break free of Assyrian oppression before the Babylonians swept behind the Assyrians. An article on Jewish Virtual Library stated that Nebuchadnezzar II was Nabopolassar's son who was fed up with the Assyrian oppression of the region. Considering the alliances between them, there was clearly some confusion about where the borders began and ended. In Ezekiel, Babylon was also stated as residing in region of the Chaldeans. In the King James version, Ezekiel references to Chaldea could be found in Ezekiel 1:3; 12:13; 23:14-23.
In Ezra 5:12, the Babylonians were stated as Chaldeans and the same verse called Nebuchadnezzar a Chaldean. Comparing the King James and NIV translations of Daniel 1:4 made it appear that the Babylonians & Chaldeans spoke the same or similar languages. Daniel 2:2-10, 3:8, 4:7 and 5:7-11, 30 recognized the Chaldeans for their knowledge of astrology. Daniel 9:1 recorded the Persians coming from the land of the Medes and taking over the land of the Babylonians, including Chaldea.
References in Habakkuk 1:6 as well as in Isaiah also confuse the Babylonians and Chaldeans (Isaiah 23:13, 43:14 and 47:1-5). Isaiah 48:14-20 prophesied against both the Babylonians and Chaldeans which aligned with Daniel 9:1.
Jeremiah once again lumped the Babylonians and Chaldeans together in the following passages:
Jeremiah 21:4-9;
22:25; 24:5;
25:21;
32:4-5,24-29,43;
33:5;
35:11; 37:5-14;
38:2,18-23;
39:5-8;
40:9-10; 41:3,18;
43:3;
51:4,24,
35,54;
52:7-17.
In Jeremiah 50:1-10,35,45, he prophesied against the Babylonians and Chaldeans just as Daniel and Isaiah did.