Note: The below post is inspired by a paper in Na’aman’s first volume, where he argues there were three Assyrian campaigns to Samaria in the 720s BC: Shalmaneser’s ravaging of Samaria in his accession year, Shalmaneser’s imprisonment of Hoshea in 723 BC, and Sargon II’s siege of Samaria and massive deportation. He uses a combination of Assyrian, Babylonian, and biblical data to come to these conclusions.
The date of the Fall of Samaria has always been something of a mystery, due to the fragmentary Assyrian and the clearly misinterpreted Israelite/Judahite records we do have. However, the chronology reign of Hoshea (732/731-723/722 BC; Israelite regnal years began in Nisan) is, in broad terms, certain. Thus, though Hezekiah clearly began his reign in Judahite Regnal Year 726 BC (Judahite regal years began in autumn), if 1 Kings 18:1-9 record reliable data, this hardly accords with the statement that he began his reign in the third year of Hoshea (unless one wishes to interpret the year-counts in Kings as counts of the total actual years, rather than new years up to that point at which the king died).
2 Kings 17
1 [In the twelfth year of Ahaz king of Judah], Hoshea the son of Elah became king over Israel in Samaria, and reigned nine years.
3 Shalmaneser king of Assyria came up against him, and Hoshea became his servant and paid him tribute.
4 But the king of Assyria found conspiracy in Hoshea, who had sent messengers to So king of Egypt and had offered no tribute to the king of Assyria, as he had done year by year; so the king of Assyria shut him up and bound him in prison.
5 Then the king of Assyria invaded the whole land and went up to Samaria [and besieged it three years].
6 [In the ninth year of Hoshea], the king of Assyria captured Samaria and carried Israel away into exile to Assyria, and settled them in Halah and Habor, on the river of Gozan, and in the cities of the Medes.
24 The king of Assyria brought men from Babylon and from Cuthah and from Avva and from Hamath and Sepharvaim, and settled them in the cities of Samaria in place of the sons of Israel. So they possessed Samaria and lived in its cities.
2 Kings 18:
1 Now it came about [in the third year of Hoshea, the son of Elah king of Israel,] that Hezekiah the son of Ahaz king of Judah became king.
2 He was twenty-five years old when he became king, and he reigned twenty-nine years in Jerusalem; and his mother’s name was Abi the daughter of Zechariah.
9 Now in the fourth year of King Hezekiah, [which was the seventh year of Hoshea son of Elah king of Israel], Shalmaneser king of Assyria came up against Samaria and besieged it.
10 [At the end of three years they captured it]; in the sixth year of Hezekiah, [which was the ninth year of Hoshea king of Israel], Samaria was captured.
11 Then the king of Assyria carried Israel away into exile to Assyria, and put them in Halah and on the Habor, the river of Gozan, and in the cities of the Medes,
Thus, we have what really happened: