The enemies of the Israelites, particularly the mighty Assyrian army, once terrified the world with their grand plans to conquer Jerusalem. Yet, the prophetic message delivered to them is sharp and mocking, revealing that their massive ambitions are nothing more than an illusion destined to end in self-destruction.
The process of plotting and executing these attacks is compared to pregnancy and childbirth. The primary approach among commentators explains that the pregnancy represents the initial stages of thought and planning, while the birth stands for the actual execution and final result. However, what these enemies plan and produce is entirely worthless. Their plots are compared to thin straw, chaff, and dry grass. These are materials that lack any real weight or value and catch fire instantly. This imagery shows that their evil thoughts are empty and their actions will ultimately fail. Taking another perspective, [אברבנאל] sees this as a reference to the false, meaningless beliefs the enemies clung to, which will inevitably lead to their ruin.
The downfall of these enemies will come directly from within themselves. The very force driving them is described as a fire that will consume them. The primary approach among commentators understands this inner drive as their malicious thoughts, desires, and schemes. The very plans they made to destroy others will transform into the fire that brings about their own end. Specifically, the plague brought upon the Assyrian camp by the angel of God is viewed as this burning fire, serving as a direct punishment for their ambition to conquer the city [רד״ק].
Other commentators offer different views on how this internal destruction unfolds. Some explain that the consuming fire represents the actual words and breath coming from the enemies' mouths. The blasphemy and insults they directed toward God will turn into a fire that burns their bodies and deeds, which are as fragile as dry straw [מלבי״ם, שד״ל]. A more physical interpretation suggests that a literal fiery wind will emerge from within their bodies to burn up the worthless chaff of their existence [רש״י]. Finally, [אבן עזרא] connects this destruction back to the earlier imagery of dry grass, noting that instead of a normal wind simply blowing the lightweight enemies away, a sudden fire will arrive to consume them completely.