The residents of Jerusalem face a stark and brutal reality. Staying within the city walls guarantees certain death, leaving only one possible path to safety: fleeing the city and surrendering completely to the Chaldean army [ביאור שטיינזלץ]. Leaving the city to approach the enemy means willingly handing oneself over to their absolute control [מצודת דוד].
This desperate act of survival is framed through the poetic imagery of gathering spoils of war [מצודת ציון]. Typically, a person advances toward an enemy army to fight and capture loot. Here, however, the dynamic is entirely different. The primary approach among commentators views this as a powerful metaphor for a person reclaiming his own existence. Just as a soldier profits from the plunder he takes in battle, the individual who defects to the Chaldeans effectively "plunders" his own life, rescuing it from the looming threats of the sword and starvation. The ultimate prize he walks away with is simply the continuation of his own life [מלבי״ם].
The promise of survival in this situation actually unfolds in two distinct, highly dangerous phases [מלבי״ם]. The first hurdle comes from within the city itself, as the guards of the King of Judah actively execute anyone caught attempting to desert. Therefore, the initial stage of survival is merely managing to escape the city limits without being killed by the king's forces. Only after successfully navigating this internal danger does the defector reach the second stage of survival. Once in the hands of the Chaldeans, the enemy will accept the surrender and spare his life, ensuring his final, enduring safety.