2 Samuel 8:4 JPS And David captured from him, one thousand and seven hundred horsemen, and twenty thousand footmen; and David houghed [IE: "hamstrung"] all the chariots [horses] and left over of them for a hundred chariots.
דוַיִּלְכֹּ֨ד דָּוִ֜ד מִמֶּ֗נּוּ אֶ֚לֶף וּשְׁבַע־מֵאוֹת֙ פָּרָשִׁ֔ים וְעֶשְׂרִ֥ים אֶ֖לֶף אִ֣ישׁ רַגְלִ֑י וַיְעַקֵּ֚ר דָּוִד֙ אֶת־כָּל־הָרֶ֔כֶב וַיּוֹתֵ֥ר מִמֶּ֖נּוּ מֵ֥אָה רָֽכֶב:
Rashi: and David houghed all the chariots (horses): because of the commandment: “He shall not multiply horses unto himself” (Deut. 17:16).
And left over of them for a hundred chariots: which he needed for his cavalry. Now a chariot consists of four horses as it is stated; “A chariot for six hundred shekels of silver and a horse for a hundred and fifty.” (II Chron. 1:17) from here it is derived that a chariot consists of four horses.
If we are talking about leaving the horse unable to stand it seems to me that that amounts to cruel and unusual punishment on an innocent animal, no?
Would he perhaps have only damaged one leg, just sufficient to keep them from being a threat? Or do we know from history or grammar that David was making a point by bringing such suffering and death on the animals?
And is there any reason he would not/could not simply keep them and re-purpose them?
IE: What were David's action and what does it tell us about our Maker and about David?
Update
I notice that Joshua was specifically commanded to hamstring the enemy horses:
Joshua 11:6 JPS And the Lord said to Joshua, "Be not afraid of them, for tomorrow at this time, I will deliver them up all slain before Israel. You shall cripple their horses, and burn their chariots with fire."
ווַיֹּ֨אמֶר יְהֹוָ֣ה אֶל־יְהוֹשֻׁ֘עַ֘ אַל־תִּירָ֣א מִפְּנֵיהֶם֒ כִּ֣י־מָחָ֞ר כָּעֵ֣ת הַזֹּ֗את אָנֹכִ֞י נֹתֵ֧ן אֶת־כֻּלָּ֛ם חֲלָלִ֖ים לִפְנֵ֣י יִשְׂרָאֵ֑ל אֶת־סֽוּסֵיהֶ֣ם תְּעַקֵּ֔ר וְאֶת־מַרְכְּבֹֽתֵיהֶ֖ם תִּשְׂרֹ֥ף בָּאֵֽשׁ: