תרועם - תשברם, והיה העי"ן ראוי להדגש לולי היותו מהגרון כמו תשוכם תסובם: You will break them (תְּרֹעֵם - tero'em): [This means] You will shatter them (teshabberem). The [letter] Ayin (ע) [the second root letter of ר-ע-ע] would properly have a dagesh (doubling dot) [in this verb stem], were it not for the fact that it is a guttural letter ("from the throat"). [This absence of an expected dagesh is] similar to [forms like] tesokhem (תְּשׂוֹכֵם) and tesovem (תְּסוֹבֵם), [where the middle root letter also lacks a dagesh].
בשבט ברזל - החרב תנפצם הפך רגשו גוים. With a rod of iron (בְּשֵׁבֶט בַּרְזֶל - be-shevet barzel): [This refers metaphorically to] the sword (ha-cherev). You will shatter them (תְּנַפְּצֵֽם - tenappetzem): [This outcome is] the opposite of (hefekh) [what the nations intended when] "nations assemble (ragshu goyim)" [in verse 1].