The rise and fall of nations often mirror the moral and spiritual state of the Israelites. When God reveals His presence, the established world order is shaken, sending waves of terror through enemy camps.
The primary approach among commentators is to view these events through the lens of the era of the Judges, highlighting a recurring cycle of sin, punishment, and repentance. During times of moral failure, God did not lack the power to save. Rather, He deliberately allowed hostile forces, such as King Cushan-rishathaim of Aram or nomadic Cushite tribes, to openly oppress the Israelites as a consequence of their actions [מצודת דוד, אברבנאל, צאינה וראינה, ביאור שטיינזלץ]. However, the moment the people repented and cried out to God, the dynamic entirely reversed. The nomadic camps of their oppressors were gripped by sudden panic. This dramatic shift points to the days of Gideon, when God sent such intense terror into the camp of Midian that the enemy soldiers ultimately turned on one another [רש״י, רד״ק, מצודת דוד, אברבנאל].
Offering a different perspective on the cause of this collapse, another interpretation suggests that the enemy camps did not fall strictly as a divine punishment for the sins of the Israelites, but because they were built on a fragile, unstable foundation of falsehood. The enemy tents collapsed because they were rooted in destruction, entirely incapable of enduring. This violent shaking of the Midianite encampments echoes the famous dream from the Book of Judges, in which a tent is seen violently overturning and collapsing before Gideon [אבן עזרא, רד״ק, מצודת ציון].
While these explanations focus on historical events, another approach projects this vision into the distant future, specifically the wars of the Messianic era. In this view, the imagery describes the future return of the Ten Tribes who were exiled beyond the rivers of Cush. Ruin will strike the Cushite nations living near these exiles. From there, the returning tribes will march to battle against the Ishmaelite nation, represented here as Midian, causing their lands to shake and tremble in the face of the approaching conflict [מלבי״ם].
Finally, an additional layer of meaning connects these events to the generation of the wilderness and the life of Moses. For a long time, the nation of Midian felt entirely secure from any Israelite threat because Moses was married to Zipporah, a Midianite who was also known as the Cushite woman. However, once Moses separated from his wife, the Midianites lost their perceived shield of protection. Realizing that a war was now imminent, sudden panic swept through their lands. Their deep anxiety was further amplified by the knowledge that a severe punishment was destined to fall upon them, a direct consequence of their role in leading the Israelites into the sin of prostitution at Shittim [אהבת יהונתן].