What do we learn from "v'Hichrati Rechev me'Efrayim v'Sus mi'Yrushalayim"?
Rashi: They will not need chariots and horses. Radak - also Michah said "v'Hichrati Susecha mi'Kirbecha v'Ha'avadti Markevosecha" (5:9). Here it mentions Efrayim and Yerushalayim, because the kingdom was divided in earlier days, but in the days of Mashi'ach, they will be united.
Malbim: Chariots are for war. Horses are for riding. People will walk to ascend to Yerushalayim; nothing Tamei (a horse is a Tamei species) will enter.
Why will "Keshes Milchamah" be cut off?
Malbim: "V'Shafat Bein ha'Goyim... Lo Yisa Goy El Goy Cherev v'Lo Yilmedu Od Milchamah" (Yeshayah 2:4). Refer to 9:10:3:1.
How will he speak Shalom to Goyim?
Radak, Malbim: He will make peace between nations, if they will have war. All nations will heed him.
What do we learn from "u'Mashlo mi'Yam Ad Yam"?
Rashi: He will rule from the [Malbim - eastern] sea until the [far] west - the end of the world.
Radak citing Ibn Ezra: This is from the south (Red) Sea until the north sea (Atlantic Ocean).
Which river is this?
Rashi: It is the Pras river.
Radak: It is the river that comes out of Eden (refer to 9:10:5:3*), at the beginning of the east, until the end of the land in the west, i.e. the entire world.
Malbim: It is the river that comes out of Eden 1 , until the end of the land, from south to north.
One river comes out of Eden (Bereishis 2:10), and it separates into four. One of the four is the Pras, which borders Bavel, which is northeast of Eretz Yisrael. It is possible that the source river is south of Eretz Yisrael. One of the rivers surrounds Kush (ibid. 13). This supports the opinion that there is a place called Kush in Asia, aside from the Kush in Africa (refer to Esther 1:1:6:2*). (PF)
