Inasmuch as this is true, they were expendable because they were (common) people and not because they were men. Hence, drafting men into war was not sexism against men.
Yeah, there is also a strong element of classism in there, but it's a mixture of both - it's because they were common people
and men. Both attributes had to apply, and the element of classism does not somehow remove the element of men being the ones expected to take the role of the defender.
That's a classic example of men becoming victims of the patriarchy.
Women demanding men to sign up for the army to defend their country purely on the basis of being men, is a clear case of sexism against men. Can't get any clearer than that.
Whether that sexism ultimately stemmed from attitudes where women were seen as too weak to fight or not, whether patriarchy is responsible for these attitudes, is completely irrelevant to the fact that the end result is that you have sexism against both, men and women.
The types of sexism are not entirely the same, because yeah, I agree with you, there is an element of seeing women as incapable that is not present on the side of men, but that is countered by the fact that men are expected to play the protector, even at their own demise.
I mean even here:
One of the most compelling arguments for feminism is that it also frees men from gendered narratives that dictate men must do manly things like fighting wars.
You're basically saying: "Feminism wants to free men from sexist expectations." (a notion that I only partly agree with), but still have to phrase it in a way that completely negates the idea that men
are - not can be, but are - victims of sexism under current circumstances although that is exactly what you are saying.
The way you simply can't admit to yourself that while women are victims of sexism, 'men are victims of sexism, too', and must instead reframe it to 'men are victims of
the patriarchy backfiring', shows exactly why feminist theory is dangerous.