Isaiah 36-39 mark the hinge of this book, the spine if you will that holds the two major halves together.
Isaiah 36-39 is different from the rest of the book. Just look at its layout. Isaiah 1-35 has been almost all poetry. Isaiah 40-66 is almost all poetry. Both sections are filled with the pronouncements of God. But 36-39 is different. It is nearly all prose and rather than be filled with divine pronouncements, it tells a story.
It is the fourteenth year of King Hezekiah.
Or is it? Sennacherib’s invasion is one of those historical dates we can determine, and it occurred in 701 B.C. But the Bible has Hezekiah ascending the throne in 729/728 B.C – the third year of Hoshea. The dates do work if we allow for a co-regency with his father Ahaz until Ahaz’ death in 714 B.C. Co-regencies were common in the ancient world. Absent information to the contrary, this possibility makes the dates work.
Chapter 36 sets up the conflict, which is not between Sennacherib and Hezekiah at all, but between Sennacherib and God. The King makes certain statements that stand out:
First, Judah has, to her discredit, not depended on God, but on her alliance with the king of Egypt, who is wholly unable to save her. Second, though she says she is depending on the Lord, this is the same Lord whose altars Hezekiah has ruined. (Here, Sennacherib betrays the fact that the doesn’t know the difference between a pagan altar and the altar of the Lord.) Third, Hezekiah cannot deliver them. And fourth (and most important of all), the Lord of Israel is simply incapable of delivering His people any more than any other god could deliver his people against Sennacherib.
These are increasingly bold statements, setting him up for a mighty fall in the next chapter.