Oh, my first downvote. Interesting. Bad Leisha, you've violated some community norm or other. But given that I'm new here and still trying to determine whether or not this community is a good fit for me, I'm curious about the specifics. I wonder what I did wrong.

A single downvote is not an expression of a community norm. It is an expression by a single person that there was something, and it could be pretty much anything, about your post that that one person did not like. I wouldn't worry until a post gets to -5 or so, and -1 isn't very predictive that it will.

Note: This post is a concerted rational effort to overcome the cached thought 'oh no, someone at LW doesn't like what I wrote :( ' and should be taken in that spirit.

The "someone at LW doesn't like what I wrote" part is accurate. You don't need the "oh no" and ":(" parts. Just because someone disagrees with you, doesn't mean that you are wrong.

Personally (and I did not vote on your post either way), I don't think you are quite engaging with the problem posed, which is that each of these hypothetical rationalists would rather win without being in the army themselves than win with being in the army, but would much prefer either of those to losing the war. Straw-man rationality, which Eliezer has spent many words opposing, including these ones, would have each rationalist decline to join up, leaving the dirty work to others. The others do the same, and they all lose the war. The surviving rationalists under occupation by barbarians then get to moan that they were too smart to win. But rationality that consistently loses is not worth the name. It is up to rationalists to find a way to organise collective actions that require a large number of participants for any chance of success, but which everyone would rather leave to everyone else.

Some possible ways look like freely surrendering, for a while, some of one's freedom. A general principle that Freedom is Good has little to say about such situations.