Chronology in 2 Kings 15

There’s a chronological problem in 2 Kings 15:1. Here’s the issue:

Amaziah of Judah reigned for 29 years (14:2).
Jeroboam II became king in the 15th year of Amaziah (14:23).
Yet, Azariah, the son of Amaziah, does not become king until the 27th year of Jeroboam II.

Hence:

Year 1 of Jeroboam II is Year 15 of Amaziah.
Year 15 of Jeroboam II is Year 29 of Amaziah, the year of his death.
Year 27 of Jeroboam II is Year 1 of Azariah.

What happened to the intervening 12 years?

The answer seems to be twofold. First, Azariah is 16 when he becomes king (15:1), which means he was a young boy (age 4) at the time of his father’s death. (His father was in his early fifties when he fathered Azariah.) Thus, there appears to be a need for some kind of regency until Azariah comes of age. It is not mentioned, but it can be inferred that Azariah did not become king fully until 13 years after his father’s death.

Second, there are a number of indications in 2 Kings 14 that Amaziah became a vassal to Jehoash of Israel after their war. Jehoash captured Amaziah (14:13), and took some hostages to exile in Samaria (14:14). Yet, Amaziah was in Jerusalem late in life (14:19). Jeroboam II restored the border of Israel as far as the “Sea of the Arabah” (14:25), the Dead Sea, which is not in the territory of the Northern kingdom. There are other indications, but that should suffice to suggest that the delay in Azariah’s kingship was not only due to his age but to the fact that he was prince of a subject people – Judah being subject to Israel during the latter part of the dynasty of Jehu. Jeroboam II was the regent for Azariah in his minority.

This perhaps also helps to explain the other anomaly in the chronology of the chapter. 15:8 says that Zechariah became king in the 38th year of Azariah. Thus:

Year 27 of Jeroboam II is Year 1 of Azariah.
Year 41 of Jeroboam II is Year 15 of Azariah; Jeroboam died in this year.
Year 1 of Zechariah is Year 38 of Azariah.

What happened to the intervening 23 years? Even if we take the 52-year reign of Azariah as dating from his father’s death, rather than his taking the throne at 16, we still have several years to account for. It seems plausible that just as the kingdom was reunited temporarily under Jehoash and Jeroboam II, so it was reunited under Azariah after the death of Jeroboam II. This is admittedly a hypothesis without explicit warrant from the text.