What is the meaning of "Ushu"?
Rashi citing Menachem: This is like Chushu (hurry).
Rashi citing Targum Yonasan: Gather. Radak - this is like "Ash Kesil v'Chimah" (Iyov 9:9) - a group of stars.
Rashi: This is like "Eshes Shen" (Shir ha'Shirim 5:14), "Barzel Asos" (Yechezkel 27:19), a mass [of iron]. The Sov is not from the root.
Why should all the nations come?
Malbim: The nations and remnant [from the second war] should all come to fight the third time, Edom against Yishmael.
What is the grammatical form of "Nikbatzu"?
Radak: It is a full command, with the Nun for the conjugation.
What do we learn from "Shamah Hanchas Hashem Giborecha"?
Targum Yonasan: There, in the gathering of Emek Yehoshafat, He will break their Gevurah. Rashi - I am unsure if Hanchas is Arame'ic (lowering 1 ), or "Chasas" (Iyov 6:21; breakage) and the Nun is omitted, like "ha'N'al l'Daniel Kadam Malka" (Daniel 2:25) - the Nun is not from the root; the root is only Al.
Radak: Giborecha are angels. This is like "Ki Mal'achav Yetzaveh Lach Lishmarcha b'Chol Derachecha" (Tehilim 91:11) and "Min Shamayim Nilchamu ha'Kochavim mi'Mesilosam Nilchamu Im Sisra" (Shoftim 5:20).
Malbim: There is no Gevurah in this war, for Hashem broke all the Giborim. There is no Gibor in existence!
Radak: The Targum of "va'Yered" (Bereishis 12:10) is v'Nachas.