Taking on a role of public leadership carries a heavy burden of responsibility for the lives of those who place their trust in that leader. When an individual is appointed to alert others of approaching danger and fails to do so, he cannot hide behind the excuse that the resulting tragedy was simply a heavenly decree. Whether driven by negligence or other calculations, a watchman who sees a threat advancing but fails to sound the horn leaves the people entirely unprepared and vulnerable [ביאור שטיינזלץ].
When someone dies in such an attack, the death is actually a consequence of the victim's own personal faults. There is a general consensus among commentators that without existing guilt, an enemy would have no power to cause harm. The exact reasons why a specific person falls in battle remain part of a private, hidden reckoning between that individual and God [מצודת דוד, רד״ק, ביאור שטיינזלץ].
Despite the victim bearing personal guilt, God still holds the watchman directly accountable for the loss of life. Even if the fallen individual ultimately deserved his fate, the watchman is punished for his failure to issue a warning. A human guard has no access to God's hidden judgments or knowledge of who is destined to die. His absolute duty is to warn everyone, simply because the community relies on him. By betraying his mission and withholding the alert, the disaster is facilitated through his hands. This dynamic illustrates a profound spiritual principle: negative decrees from heaven are often brought into reality through the actions of someone who is already acting improperly or negligently [מצודת דוד, רד״ק].
On a deeper moral and spiritual level, the duty of the watchman extends far beyond merely spotting a physical weapon or advancing army. It includes the vital obligation to guide and correct the people. Had the leader spoken up and inspired the community to repent, they might have been spared entirely. Because of this, his silence directly implicates him in the tragic outcome [מלבי״ם].