(ט) וַיִּתֵּ֥ן יוֹאָ֛ב אֶת־מִסְפַּ֥ר מִפְקַד־הָעָ֖ם אֶל־הַמֶּ֑לֶךְ וַתְּהִ֣י יִשְׂרָאֵ֡ל שְֽׁמֹנֶה֩ מֵא֨וֹת אֶ֤לֶף אִֽישׁ־חַ֙יִל֙ שֹׁ֣לֵֽף חֶ֔רֶב וְאִ֣ישׁ יְהוּדָ֔ה חֲמֵשׁ־מֵא֥וֹת אֶ֖לֶף אִֽישׁ׃
Joab reported to the king the number of the people that had been recorded: in Israel there were 800,000 soldiers ready to draw the sword, and Judah’s contingent numbered 500,000.
(The above rendering comes from the RJPS translation, an adaptation of the NJPS translation. Before accounting for this rendering, I will analyze the plain sense of the אִישׁ term, by employing a situation-oriented construal as outlined in “Notes on Gender in Translation,” pp. 11–16.)
This usage of אִישׁ is conventional: it profiles the referent as a distinct entity within a larger military force, here under David’s unified command.
On the regular usage of singular אִישׁ as a “collective” term in the context of hostilities, see my comment to Judg 7:23. On its occasional use to denote a contingent of military forces, see my comment at Judg 7:24.
As for rendering into English, the NJPS ‘the men of Judah’ misses the situational nuances. On properly rendering the collective usage of אִישׁ into idiomatic English, see my comment at Josh 10:24.