B'midbar 32:17 - Why did the tribes of Re'uven and Gad need to build fortified cities?

Question

Numbers 32:17:

וַאֲנַ֜חְנוּ נֵחָלֵ֣ץ חֻשִׁ֗ים לִפְנֵי֙ בְּנֵ֣י יִשְׂרָאֵ֔ל עַ֛ד אֲשֶׁ֥ר אִם־הֲבִֽיאֹנֻ֖ם אֶל־מְקוֹמָ֑ם וְיָשַׁ֤ב טַפֵּ֙נוּ֙ בְּעָרֵ֣י הַמִּבְצָ֔ר מִפְּנֵ֖י יֹשְׁבֵ֥י הָאָֽרֶץ׃

but we ourselves will be ready armed to go before the children of Israel, until we have brought them unto their place; and our little ones shall dwell in the fortified cities because of the inhabitants of the land.

What inhabitants of the land? I thought the land was completely conquered and there was no on left!

Didn't Re'uven and Gad themselves say?

Numbers 32:4:

הָאָ֗רֶץ אֲשֶׁ֨ר הִכָּ֤ה יְהוָה֙ לִפְנֵי֙ עֲדַ֣ת יִשְׂרָאֵ֔ל אֶ֥רֶץ מִקְנֶ֖ה הִ֑וא וְלַֽעֲבָדֶ֖יךָ מִקְנֶֽה׃

the land which the LORD smote before the congregation of Israel, is a land for cattle, and thy servants have cattle.’

It also says:

Deuteronomy 2:34:

וַנִּלְכֹּ֤ד אֶת־כָּל־עָרָיו֙ בָּעֵ֣ת הַהִ֔וא וַֽנַּחֲרֵם֙ אֶת־כָּל־עִ֣יר מְתִ֔ם וְהַנָּשִׁ֖ים וְהַטָּ֑ף לֹ֥א הִשְׁאַ֖רְנוּ שָׂרִֽיד׃

And we took all his cities at that time, and utterly destroyed every city, the men, and the women, and the little ones; we left none remaining;

So, why the need to fortify any cities if there were no land inhabitants?

Counter-question - if they were afraid of the inhabitants, the men are going to war leaving the women and children vulnerable to them, even if they are in a fortified city. (How strong could it actually have been?) Who was protecting them?

Answer 1

The Art Scroll Chumash on Mattos 32:16 cites Abarbanel who says that they intended to rebuild and refortify the cities. I have seen in a number of places that had they left those remaining behind defenseless, the "inhabitants of the land" surrounding the areas captured would have moved in and conquered the areas occupied by Reuven and Gad.

The Art Scroll Chumash commentary on Devarim 2:34 cites Ramban that, the cities of Sichon were occupied by the Amorites who were subject to the command of 20:16 that no survivors were to be left. However, the nonAmorites surrounding them were still there.

Note that only the best fighters were required to cross the Yarden. They did have regular fighters as well as the retired fighters and the youngsters not yet in the army. They would need to be able to defend the cities against attack from outside.

The youngsters just under military age seasoned by a skeleton force and trained by the "retirees" would be enough to defend the cities and prevent invasion and raiding of the flocks.

Answer 2

Divrei Hayamim I 5:10 and 5:19-22 mentions a war between the two and a half tribes and the "Hagarites" in the time of Shaul (and there's a Midrash - right now I don't remember the location - that says that actually it was in the time of Yehoshua). So even if the Emorites were wiped out, there were certainly other dangerous tribes and nations.