The sudden collapse of an entire kingdom often hinges on a single, fatal military decision. In the campaign against the Amorites, the victory was incredibly fast and absolute. Because King Sihon chose to march his entire army out to the open battlefield to confront the Israelites, he left his fortified cities practically undefended. This strategic error allowed the Israelites to capture the cities immediately, bypassing the need for long sieges [הכתב והקבלה, מלבי״ם].
Once the cities fell, the Israelites carried out a total destruction of the population. Since these cities belonged to the Amorite nation, this action fulfilled God's direct command to wipe out the seven Canaanite nations, leaving no survivors. However, this devastating outcome was not the first resort. The total annihilation of the population was only enacted after Sihon firmly rejected the initial peace offer sent to him [רמב״ן, הטור הארוך, רש״ר הירש, ביאור יש״ר].
While the fate of the people was sealed, commentators debate what happened to the cities themselves. Some explain that the Israelites physically leveled the cities to the ground [ביאור שטיינזלץ]. Others argue that the buildings and infrastructure were left intact, as they were intended for future Israelite settlement. According to this view, the destruction applied strictly to the enemy population, emptying the cities of their inhabitants rather than destroying the physical structures [הכתב והקבלה].
The primary approach among commentators is that the victims within the cities were the men, women, and children [רש״י, אבן עזרא, ביאור שטיינזלץ]. Yet, an interesting discussion arises regarding the nature of the men who remained in the cities. One perspective suggests that these individuals were actually warriors of great strength and bravery, highlighting the Israelites' power in defeating the enemy's most excellent fighters [העמק דבר, שד״ל]. Conversely, another approach argues that because the true heroes of the army had already marched out to the battlefield with Sihon, the men left behind in the cities were actually weak and unfit for combat, making them exceptionally easy to subdue [מלבי״ם]. Regardless of their strength, the final result was exactly the same. The men, along with all the women and children, were completely wiped out, leaving no trace of a survivor behind [ביאור שטיינזלץ].