Marduk-apla-iddina II (cuneiform spelling ᴰMES.A.SUM-na; in the Bible Merodach-Baladan, also called Marduk-Baladan, Baladanand Berodach-Baladan, lit. Marduk has given me an heir) was a Chaldean prince who usurped the Babylonian throne in 721 BC and reigned in 722 BC--710 BC, and 703 BC--702 BC.
Marduk-apla-iddina II was known as one of the kings who maintained Babylonian independence in the face of Assyrian military supremacy for more than a decade.
Sargon of Assyria repressed the allies of Marduk-apla-iddina II in Elam, Aram and Israel and eventually drove (ca. 710 BC) him from Babylon. After the death of Sargon, Marduk-apla-iddina II briefly recaptured the throne from a native Babylonian nobleman. He reigned nine months (703 BC – 702 BC). He returned from Elam and ignited rebellion in Babylonia. He was able to enter Babylon and be declared king again. Nine months later he was defeated near Kish by the Assyrians, but managed to flee to Elam. He died in exile a couple of years later.
Merodach-baladan is mentioned as king of Babylon in the days of King Hezekiah, both in 2 Kings 20:12 (here called Berodach-baladan) and in Isaiah 39:1. In both passages he sends Hezekiah a letter, having heard of his illness and recovery. His messengers who have delivered the letter are lavishly entertained by Hezekiah, leading the prophet Isaiah to criticise Hezekiah for his excessive openness about the wealth he had amassed.