Why will Cheshbon lament over Ai?
Rashi: It is nearby; it is from Amon.
Radak: Cheshbon used to be of Mo'av after Bnei Gad and Bnei Reuven were exiled in Bayis Sheni 1 , and Ai was of Amon. There was another Ai in Eretz Kena'an. when Nebuchadnetzar ascended to the land, first he inundated Amon, and afterwards Mo'av. When he came to Amon, he first encountered Ai. Even though you, Cheshbon, are a great fortified city, lament. Since Ai, which was fortified, was plundered, [also] you will not be saved.
Malbim: The enemy came to Cheshbon via Ai of Mo'av.
Surely it should say 'Rishon', even though I did not find such a text. Radak himself says in several places (Yo'el 4:19, Zecharyah 8:19, Divrei ha'Yamim I, 9:1) that the 10 tribes did not return in Bayis Sheni! (PF)
Who are "Bnos Rabah"?
Rashi: The people of Rabas Bnei Amon.
Radak: The village of (near) Rabas Bnei Amon. Malbim - this is like "u'Vnoseha ba'Esh Titzasnah" (verse 2).
Why should Bnos Rabah scream?
Malbim: From Ai and Cheshbon, the enemy will come to Rabah.
What is the meaning of "v'Hisshotatnah ba'Gederos"?
Rashi citing Targum Yonasan: They will be confounded with camps 1 - i.e. assemblies of troops. Hisshotatnah is an expression of soldiers who are Meshotet (prowl). Gederos is an expression of "Gidros Tzon" (Bamidbar 32:16), pens full of flocks.
Rashi: Hisshotatnah is like His'olalnah in excrement of pens of flocks. It is an expression of soldiers who are Meshotet (prowl). Gederos it is an expression of "Gidros Tzon" (Bamidbar 32:16), pens full of flocks. It is an expression of disgrace. The Targum of "va'Yivez Esav" (Bereishis 25:34) is v'Tash Esav.
Radak: This is like "mi'Shot ba'Aretz" (Iyov 1:7). I.e. go here and there - people are screaming and eulogizing. Gederos refers to enclosures of the villages. They are not called walls, rather, Gederos, like "Gidros Tzon" (Bamidbar 32:16), or Gidros of gardens and the Karmel. They do not make fortified walls for villages. He says to them, go among yourselves in your Gidros. Do not think to be protected in a walled city with doors and a bolt. It will not help you; also it will be conquered. "Malkam ba'Golah Yelech" - their king sits in Rabah, the capitol. (He will be exiled, even though it is fortified.)
Malbim: They will go around in pens, for they will not have houses; they will be destroyed.
Radak: This is astounding. Yonason translated also "Al Kol Yadayim Gedudos" (48:37) like this. It seems that his text here was not "Gederos", rather, Gedudos.
