Moments before a battle begins, an army must transform from a collection of individuals into a united, disciplined fighting force. After those granted military exemptions have safely returned home, the remaining soldiers face a critical reorganization. This stage is designed to build a cohesive, highly motivated unit guided by a clear chain of command [שטיינזלץ].
Even though the soldiers are promised divine protection in battle, they are instructed to prepare using entirely natural military tactics. The primary approach among commentators is that God operates within the boundaries of nature and keeps His miracles hidden. He does not alter the natural order of the world except in extreme situations where there is no other choice, or to make His name known, such as during the splitting of the Red Sea [רמב״ן, הטור הארוך, רבינו בחיי, ביאור יש״ר].
Establishing this leadership structure occurs specifically at this moment, after the exempt men have left. This timing ensures that the sight of soldiers heading home does not discourage the remaining fighters or weaken their morale [ספורנו]. Interestingly, the exemptions granted for building a new home, planting a vineyard, or becoming engaged serve an additional purpose. They provide a convenient cover for those who are actually leaving the front lines out of fear because of their past sins, allowing them to return home without facing public shame [גור אריה]. As the army reorganizes, most commentators understand that new commanders are officially appointed to lead the troops [אבן עזרא, חזקוני, רבינו בחיי, שטיינזלץ]. However, another perspective suggests that this process involves conducting a strict census of the soldiers before the clash, allowing the leadership to later track the exact number of casualties and captives [ביאור יש״ר].
The newly appointed commanders are tasked with much more than standard military strategy; they bear the heavy responsibility of maintaining strict discipline and preventing desertion. To achieve this, they position strong guards at both ends of the battlefield. At the front lines, personnel are stationed to physically support fallen soldiers and encourage them to keep fighting. At the rear, guards stand watch holding iron weapons and axes [רש״י, ברכת אשר, תורה תמימה]. This comprehensive security ensures that the troops are monitored from the front to the back [תורה תמימה].
Discipline is enforced with absolute severity. If a soldier attempts to flee the battlefield after the final announcements are made and the exempt men have departed, the guards are authorized to strike him or even sever his legs to stop his retreat [רש״י, דברי דוד, אדרת אליהו]. This harsh measure stems from the understanding that fear is highly contagious. Every military defeat and collapse on the battlefield begins with panic, fleeing, and the breaking of ranks [רש״י, שפתי חכמים, מלבי״ם, רלב״ג].
It is important to note that this specific system of rules and exemptions applies exclusively to an optional war. In the case of an obligatory war, every single person is required to go out and fight, without any exceptions [רלב״ג, מלבי״ם].
Beyond the literal military preparations, some view the appointment of these leaders as a hint to divine oversight, suggesting that heavenly commanders provide spiritual assistance to the Israelites [רבינו בחיי]. Others see the entire battlefield setup as a powerful metaphor for the internal, spiritual war a person fights against their own negative desires and the forces of impurity [אלשיך].