The joy of salvation is often best understood through the feeling of a sudden, immense weight being lifted off one's shoulders. The political subjugation of the Kingdom of Judah to the Assyrian empire, and its miraculous liberation by God, is vividly illustrated through the imagery of farm labor and beasts of burden. The primary approach among commentators is that this focuses on the crushing taxes and subjugation imposed by the Assyrian king on Judah and King Hezekiah. This bitter reality began a generation earlier when Hezekiah's father, Ahaz, started paying regular tribute to Assyria [שד״ל]. The nation is compared to a beast of burden whose cruel owners overload it without mercy [מלבי״ם, שד״ל, אברבנאל]. The heavy load represents the severe taxes and the deep suffering they caused [רש״י, רד״ק, אברבנאל, מצודת ציון, שד״ל].
The tools of this oppression are described in vivid detail. The staff on the shoulder is understood either as a stick used to strike the beast to force it to work faster [אבן עזרא, שד״ל], or as the heavy yoke itself resting on the animal [שטיינזלץ]. The rod of the oppressor represents the whip wielded by the cruel ruler [מצודת ציון, שד״ל, שטיינזלץ]. While some view these multiple descriptions of beating and subjugation simply as poetic language [מצודת דוד], others see a precise breakdown of the oppression. For example, [מלבי״ם] divides the suffering into three distinct layers: the yoke is the crushing tax itself, the staff is the cruel king demanding payment, and the rod is the Assyrian army enforcing his harsh decrees.
God completely smashed and shattered this entire system of oppression in a single moment [מצודת ציון, שד״ל, אבן עזרא]. This sudden breaking is compared to the historical defeat of Midian by Gideon. The commentators agree on this connection due to striking parallels. First, both were miraculous victories where a tiny force overcame massive, countless armies through the spirit of God rather than standard military power [רד״ק, אברבנאל]. Second, in both events, the enemy was destroyed without an actual battle; the Midianites panicked and turned on each other, while the Assyrian soldiers were struck down by an angel [שד״ל]. Finally, both complete and sudden downfalls occurred overnight. Rabbinic tradition even notes that both miraculous nights took place on the exact same date, during the spring harvest on the holiday of Passover [רש״י, מצודת דוד, מלבי״ם, שד״ל, אברבנאל].