In this chapter, Ahaz becomes king and leads Judah into disaster.
This chapter is much longer than the previous chapter, but unfortunately the reason it's longer is because there are so many bad things to talk about.
The life of Ahaz marks a turning point in Judah's history. In the past, Judah's history was predominantly centered around their relationship with Israel (I am only referring to their history after the kingdom was divided in the life of Rehoboam). There was a long sequence of events that began with Jehoshaphat's alliance with Ahab and concluded when Athaliah was killed by Jehoiada and Joash ascended to the throne. Even after that, Amaziah was torn apart by an unsuccessful battle against Israel.
Amongst other things, the text gives us a sense that Israel is generally stronger than Judah. We see this in the nature of Jehoshaphat's relationship with Ahab (where Ahab is the one directing their battles and course of action). We see that in 2 Chron 16:1-6 where Israel came to blockade Judah and king Asa could not remove them by force. Even when Abijah defeated Israel in 2 Chron 13, it comes across as a victory by miracle rather than a victory by strength. The obvious implication is that Israel was stronger than Judah. Even in this chapter, Israel comes in and smashes Judah again.
However, in the near future we are going to see Israel decline and fall at the hands of the Assyrians. Israel will stop being the primary enemy for Judah, and instead Judah will begin fighting most of their battles against the Assyrians (and later, the Babylonians). We already see this beginning to happen at the end of the chapter when the Assyrians come and add to the oppression of the Judeans.
Another thing we will see in this next period (beginning here with Ahaz) is interlocking waves of religious revival and decline. In this chapter with Ahaz we begin with a tremendous decline, but it will be followed by a major revival, followed by a major decline, followed by ANOTHER major revival, followed lastly by decline and exile. It comes and goes in waves, often between father and son. In this case, Ahaz's father was generally a godly man, and his son Hezekiah is one of the best kings of Judah in the post-Solomonic era, but Ahaz himself is a wretched king. These powerful religious waves (in both directions) combined with the persistent military conflicts leave Judah in a position of great turmoil and strife between now and the exile to Babylon. Remember back in 2 Chron 14:6 when God gave Asa rest? Peace and rest was one of the major themes of Asa's reign. In contrast, this next era will be a period of conflict.
I don't want to make it sound like Judah was in constant warfare from a historical perspective. We can tell from the biblical narrative that many of these kings ruled for long periods without active conflict. At the same time, I do think the biblical narrative is written with an emphasis on the military conflicts during this period.
Furthermore, when Judah loses battles the results are becoming more devastating. In this chapter the Israelites are so brutal towards their Judean neighbors that a prophet of the LORD comes out and rebukes them for it. The Israelites kill 120,000 soldiers and attempt to enslave another 200,000 people. These are staggering numbers for a kingdom that may have only had a population of a couple million people in total.
All of these factors are present in the current chapter. We see a rapid religious decline under Ahaz that is punctuated with numerous military defeats against both Aram/Assyria and Israel. Indeed, verse 5 points out that the military losses are a direct result of Ahaz's idolatry in verses 2-4, so these two issues are interconnected. Verse 19 reiterates that Judah was "humbled" in defeat because of Ahaz was unfaithful to God.
In verse 22, Ahaz faces a challenge similar to what Saul faced all the way back in 1 Samuel 13. In that chapter, Israel was being invaded by the Philistines, his enemies were gathering, and Saul's own men were scattering. When the pressure built up, Saul broke God's command and offered a sacrifice not because God wanted it (Saul was forbidden to offer sacrifices since he was not a priest), but Saul offered a sacrifice as an attempt to rally his troops and raise morale. What we often see in the bible is that times of pressure reveal the true nature of a man's heart.
Saul showed his true nature was seeking the approval of men. Later, David is under deep pressure and in that place he strengthened himself in the LORD his God (1 Samuel 30:6). David showed his true nature was to seek God in the midst of deepest darkness. In this chapter, Ahaz is under tremendous pressure and he shows that his true nature is to seek and worship power. The Assyrians were the most powerful kingdom at the time and in the moment of Ahaz's greatest darkness, he turns to worship and obey other gods because he hopes that they will strengthen him and make him powerful like the Assyrians.
The message from this chapter is that Ahaz is wrong to hope the gods of the Assyrians will help him, because he is mistaken in his belief that the gods of the Assyrians are helping the Assyrians. The gods of the Assyrians have no power to help anyone. Only the LORD has the power to raise up one nation and tear down another, and by forsaking the LORD and worshiping idols, Ahaz is only accelerating his own decline.
This pattern will emerge in the following chapters as well: religious decline almost always coincides with military defeat and religious revival almost always coincides with military victory.
In the next chapter, Hezekiah becomes king and introduces revival to Judah, undoing much but not all of the damage that Ahaz inflicted.