What is "Bik'am Haros ha'Gil'ad"?
Rashi: They destroyed them and cleaved their pregnant women 1 , so no heir will remain to contest the inheritance. So it says "li'Vnei Amon Ko Amar Hashem ha'Vanim Ein l'Yisrael Im Yoresh Ein Lo Madu'a Yarash 2 Malkam" (Yirmeyah 49:1).
Radak #1, Malbim citing Mahari: Bnei Amon borderer Gil'ad. They cleaved mountains in order to widen their borders. Radak ? moving the borders is a great sin ? one of the curses in the Torah is "Arur Masig Gevul Re'ehu" (Devarim 27:17)! Haros is the feminine plural of Har 3 .
Radak #2: Haros are their fortified cities ? "v'Haroseihem Tevaka" (Melachim II, 8:12), "Hineni Elecha Har ha'Mashchis" (Yirmeyah 51:25). It says "li'Vnei Amon? Madu'a Yarash Malkam Es Gad?" (Yirmeyah 49:1). Gad and Gil'ad (mentioned here) were in Ever ha'Yarden.
Radak #3: This is like "he'Haroseha Bike'a" (Melachim II, 15:16), "v'Hariyosav Yevuka'u" (Hoshe'a 14:1). This was amidst lack of mercy on them ? "Oleleihem Yerutashu" (ibid). They killed the infants and cleaved the pregnant women ? all the more so they killed [all] others! This was "Lema'an Harchiv Es Gevulam" - so no remnant will remain in Yisrael.
Malbim: "Madu'a Yarash" hints to cutting off the children, who inherit. The end of the verse "Es Gad v'Amo b'Arav Yashav" hints to widening their borders.
Radak did not explain this. Har is always masculine! (PF)