>There should be a default but omitted noun, just like we say Češka, Poljska and Turska for Czech, Poland and Turkey - all of them adjectives, but with an assumed noun (country) to them. Somehow I expect "the military" to be a plural, just like "the poor".
>
>Soldiers?

There is no plural of soldier. There are only troops, remember? Soldiers is not politically correct (don't ask me why).

>I don't actually have a problem with "the military" as a collective noun there.

Neither have I, with using an adjective as a subject, as long as there is an implied noun. In this case, it's a military... what?