In Egypt's most critical hour of need, the defense systems it relied upon completely collapse, and its strongest pillars of support prove useless. The exact identity of these failed defenders is debated. They may have been foreign mercenaries and allied kings hired specifically to aid Egypt in battle [רד״ק, מלבי״ם, ביאור שטיינזלץ]. Alternatively, they might have been Egypt's own high-ranking and honored princes [רש״י, מצודות].
Regardless of their identity, these forces are compared to fatted calves kept in a stall. This imagery points to how they comfortably sat, ate, and drank from Egypt's wealth, yet grew lazy and failed to actually fight when the time came [רד״ק, צאינה וראינה]. Just as fatted calves are ultimately raised for the slaughterhouse, these warriors were being led straight to their doom [מצודת דוד]. Adding a spiritual layer to this comparison, the mercenaries worshipped the same bull idol as the Egyptians. Because they shared this false worship, their destinies became intertwined, causing them to fall together as a single nation [אהבת יהונתן].
When the war finally broke out, these fighters simply turned their backs and fled. Although military leaders and warriors are expected to be brave and hold their ground, they completely lost their nerve. Because they ran away, they were struck down and killed when the enemy eventually caught them, instead of being taken alive as captives, which was the standard practice for defeated nobles [מצודת דוד].
This total collapse occurred because their destined day of disaster had arrived, bringing ruin, misfortune, and death [מצודת ציון]. The downfall is described as a combination of two distinct forces coming to a close. The day of disaster represents the natural end of the era allotted for their worldly success. At the same time, the time of punishment represents the exact moment of divine judgment, when God stepped in to penalize them for their sins. Together, the end of their natural success and the active punishment from God sealed their final defeat [מלבי״ם].