The powerful Babylonian empire, led by Nebuchadnezzar, stands at the absolute peak of its arrogance and destructive force. For this conqueror, mere military victory is not enough. Defeating world leaders and shattering mighty fortresses is so effortless that it becomes a constant source of amusement and mockery.
As he conquers, he continuously scorns and ridicules the defeated kings [רד״ק]. His own sense of glory is fueled entirely by humiliating these monarchs [אברבנאל], and he offers them no respect even if they surrender willingly [מלבי״ם]. High-ranking ministers, rulers, and royal advisors are reduced to a mere joke in his eyes. He has absolutely no need for their counsel or assistance [מלבי״ם], and the act of killing or exiling them brings him tremendous joy and laughter [אברבנאל].
Flesh-and-blood leaders fail to deter him, and stone walls fare no better. He laughs at every stronghold, easily overtaking the highest and most heavily guarded cities without ever needing to endure a long, drawn-out siege [מצודות, מלבי״ם, אברבנאל].
The sheer ease of these conquests is illustrated through the image of gathering dirt. The primary approach among commentators is to view this as a tactical description of Babylonian siege warfare. The massive army collects enormous amounts of earth to construct a towering siege ramp against the city defenses. By fighting from atop this high mound, or by using the dirt to fill in the defensive trenches surrounding the walls, they capture the city with ease. Alongside this practical military explanation, some view the imagery metaphorically. The gathered dirt represents the overwhelming size of the conquering army, assembled in numbers as vast as the dust of the earth [רד״ק]. Another perspective suggests it is a poetic illustration of absolute dominance, as though the conqueror simply scoops up all the dust of the earth in his hands, effortlessly capturing every fortress in his path [אבן עזרא].