וְדָוִ֖ד בָּ֣א מַחֲנָ֑יְמָה וְאַבְשָׁלֹ֗ם עָבַר֙ אֶת־הַיַּרְדֵּ֔ן ה֕וּא וְכׇל־אִ֥ישׁ יִשְׂרָאֵ֖ל עִמּֽוֹ׃
David had reached Mahanaim when Absalom, and Israel’s entire force with him, crossed the Jordan.
(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.)
When a referring expression includes אִישׁ, that noun prototypically marks its referent’s defining participation in the depicted situation. This remains true when אִישׁ is in construct with a group name, such as אִישׁ יִשְׂרָאֵל. Here, in the context of intragroup hostilities, it labels the militia in terms of their being a constitutive party to the coup d’état. The militia’s members are construed as a unit—hence the singular noun. This usage regards them as one of the two opposing sides. This is one of the instances where a “collective” construal of אִישׁ is evident grammatically, from the application of the quantifier כׇל.
On the meaning of this conventional usage in the context of hostilities, see further my comment at Josh 10:24.
As for rendering into English, see my comment at Josh 10:24. Meanwhile, the fact that women are not in view is self-evident from the military context.