ירמיהו, פרק נ״א, פסוק נ״ח

The absolute downfall of an invincible empire is realized when its physical defenses collapse and human effort becomes entirely pointless. God's decree seals the fate of the mightiest structures, turning massive labor into ashes. Babylon was protected by a complex system of inner and outer walls, each exceptionally wide and strong. Yet, this immense strength will offer no protection [רד״ק, מצודת דוד]. The destruction will be so absolute that it will shatter the structures completely, uprooting them to the point of exposing their very foundations [רש״י, מצודת ציון, מלבי״ם]. At the same time, the city's towering gates will be set ablaze and consumed by fire [רד״ק, מצודת ציון].

This total ruin brings deep despair to the many nations connected to the empire, who will face an overwhelming, persistent wave of emptiness and fire [רד״ק, מצודת ציון]. The nature of their wasted labor is understood in several complementary ways. From a historical perspective, the nations will suddenly realize that all their past work in developing and building the city was entirely in vain, as everything they built is destined for the flames [רד״ק, ביאור שטיינזלץ].

During the destruction itself, this pointless effort will manifest in the immediate reactions of the people. The nations present in the city will fight the invading enemy with intense effort, but with zero success [מצודת דוד]. In a desperate attempt to save their empire, some will struggle to physically support the collapsing walls, while others will try to put out the flames. Ultimately, this massive struggle against an all-consuming fire will leave them completely exhausted, entirely unable to save the city [מלבי״ם, מצודת דוד, ביאור שטיינזלץ].