The ultimate downfall of arrogant and oppressive powers is not a sudden accident, but a destiny set long in advance. God's judgment against the Assyrian army and its king is captured through the vivid imagery of a massive, unquenchable fire. This punishment was arranged and decreed long before the actual events took place [מצודת דוד, אבן עזרא, אברבנאל, רד״ק]. A midrashic perspective traces this preparation all the way back to the second day of creation, noting it is the first day in history that had a yesterday but no day prior [רש״י, אברבנאל].
The specific site of this punishment carries deep symbolic weight. The primary approach among commentators is that it refers to Gehenna, the spiritual realm of punishment for the wicked who were lured by their own desires [רש״י, מצודת ציון, רד״ק]. Conversely, others view it as a distinctly physical location. It may refer to a polluted area surrounding Jerusalem where refuse was constantly burned, creating a perpetual pillar of smoke [אבן עזרא]. Alternatively, it points to the Valley of Hinnom, the notorious site of idolatrous child sacrifices. This location earned its name from the drums beaten to drown out the cries of the victims offered to the idol Molech [שד״ל].
This site of destruction was specifically designated for the Assyrian king, Sennacherib, and his vast military camp [רש״י, מצודת דוד, אבן עזרא, רד״ק, אברבנאל, שטיינזלץ]. The designation for the king introduces a dark irony, creating a play on words with the idol Molech once worshipped in that very valley [שד״ל]. Adding to this historical irony, Sennacherib had originally prepared the site to sacrifice his own sons to his gods. Instead, the pyre he built became his own deadly trap when his sons preemptively assassinated him there [מלבי״ם].
To accommodate the sheer size of the Assyrian forces, God made the burning expanse incredibly deep and wide, filled with an abundance of wood [מצודת דוד, רד״ק]. Yet, this massive blaze is not sustained by physical fuel alone. It is ignited and driven by the very breath of God. His will fans the flames like a rushing stream of sulfur, ensuring the fire burns fiercely and cannot be extinguished [רש״י, מצודת דוד, אברבנאל, מלבי״ם]. Ultimately, this raging inferno serves as a powerful metaphor for the sudden plague, swift decrees, and severe afflictions that devastated the Assyrian army through a direct Divine command [מצודת דוד, אבן עזרא, רד״ק, אברבנאל].