An unnatural alliance forms when nations that typically despise one another suddenly find a unifying cause. Enemies bridge their deep internal divides to gather with a single mind, heart, and voice [אבן עזרא, ביאור שטיינזלץ]. Nations that routinely wage war against each other willingly set aside their bitter hatred to unite against the Israelites [רד״ק]. This coalition is highly unusual because it brings together a diverse mix of neighboring and distant lands. Under normal circumstances, neighboring countries fight out of fear or a desire to conquer territory, while distant nations attack to gather loot. In this case, however, they abandon their standard political and economic interests to rally around one shared purpose [מלבי״ם].
The primary approach among commentators is that this military campaign is not merely a political conflict, but a direct war against God [מצודת דוד, אלשיך, ביאור שטיינזלץ]. The nations forge their pact fueled by the heretical belief that God is powerless to save His people from their combined strength [רד״ק]. The deep motive driving this campaign of destruction is a profound jealousy of the divine revelation that enters the world specifically through the Israelites [מלבי״ם].
The attackers fully understand the deep bond between the Creator and His nation. Wiping out the Israelites is a calculated attempt to erase God's name and His unique presence from human memory [רש״י, אבן עזרא, מאירי]. Because God is intimately known as the God of Israel, the enemies believe that if the nation is forgotten, His great name will no longer be recognized on earth [רש״י]. Consequently, an attack on the people is considered a direct strike against God Himself, for in their distress, He suffers alongside them [מאירי].