במדבר, פרק כ״א, פסוק כ״ג

A peaceful request for safe passage through foreign territory is met with a harsh and unexpected military response. Rather than simply blocking the Israelites from entering, the Amorite king mobilizes his entire army for a frontal assault outside his borders. This aggressive reaction stands in sharp contrast to the king of Edom, who previously settled for merely denying entry. The primary approach among commentators is that Sihon functioned as a hired border guard for the kings of Canaan. Because they paid him a regular tax to block foreign invasions, he felt obligated to launch a proactive war to justify his salary and prevent the Israelites from reaching Canaan from any direction [רש״י, גור אריה, משכיל לדוד, דברי דוד]. On the other hand, some explain that Sihon deeply despised the Israelites and denied the miracles God had performed for them. He marched out proudly to show surrounding nations that there was nothing to fear and that the Israelite God lacked the power to save them [ביאור יש״ר]. Another perspective suggests that the gentle and polite nature of the Israelites' request was exactly what provoked the attack, as Sihon interpreted their manners as a sign of weakness [ביאור שטיינזלץ]. Ultimately, his refusal was absolute, denying them passage even at the very edge of his territory [בכור שור].

Sihon's military strategy appears highly illogical. He abandoned his fortified capital city of Heshbon, a stronghold so notoriously secure that tradition claims it could not be conquered even if it were defended by nothing more than weak mosquitoes. Instead of remaining safe behind massive walls, the king gathered his people and marched out into the open desert. Most commentators agree that this move was not driven by military tactics, but by Divine intervention. God placed it in the hearts of Sihon and his men to leave their secure towns and gather in a single vulnerable location. This miracle spared the Israelites the immense effort and danger of a prolonged siege on every individual city. By defeating the entire army in one open battle, they could easily walk into the remaining undefended towns [רש״י, שפתי חכמים, מזרחי, ברטנורא]. Alternatively, the army marched into the desert simply because that was where the Israelites were camped at the time [חזקוני]. Another explanation is that the battle was drawn out into the desert to prevent the land itself from being defiled by casualties. This ensured that the territory, which would later be inherited by the tribes of Reuben and Gad, remained pure [שפתי כהן].

The forces clashed at the city of Jahaz [אבן עזרא, ביאור שטיינזלץ, ביאור יש״ר]. The fact that Sihon initiated the violence is significant; the moment the enemy launched an unprovoked attack, the Israelites were bound by a commandment to defend themselves and fight back [קונטרס חיבה יתירה]. This battle was fought through natural, conventional warfare with swords, serving a crucial psychological purpose for the Israelites. Winning a direct, frontal war built their confidence for the upcoming conquest of Canaan, proving they could hold their ground against the thirty-one Canaanite kings. At the same time, witnessing the Israelites fight in a conventional, worldly manner caused the kings of Canaan to unite in preparation for their own impending war [שפתי כהן].