I've been at this for a few years, and I like to think that I have an at least competent (if not skilled or proficient) grasp of the game... except in military matters, since I've never managed to really form one and get it to do anything. That's planning to change this time around, but there are a few things I'd quite like cleared up first.
1) I used to like to try giving my military dwarves leather shirt and trousers under their armor, but then I ended up using a civ that doesn't have shirts... in fact the only upper body clothing they had was dresses (and cloaks, of course). "Okay," I think to myself, "I can't really imagine how they'd be able to wear a dress under their armor, but it *is* on the 'under' layer according to the wiki, and look at that coverage!" Unfortunately, I never got to test this out, since I got tired of that fortress before actually setting up a military, but the question remains: can Dwarves wear dresses under armor, and does it only count as upper body slot-wise, or can they wear trousers at the same time?
2) Leather is a pain to produce. Almost all of mine comes from either trading with caravans, or locking up a bunch of fowl to let their eggs hatch, then slaughtering the lot. Add to that, I need it for backpacks and quivers, and sometimes possibly light armor to go under the mail (my glass industry nearly every game is well up to the task of making vials though, so no waterskins). Fabric, by contrast, I can make a ton of - the question is, then, is it worth it to get leather clothes on my dwarves under their armor at all, or is cloth "good enough" to use instead? Even if I do end up with cloth clothes, what about the cloaks - is a leather cloak that much better than a cloth one?
3) Obsidian short swords. Are they remotely good? Relates directly to 4.
4) Is there a way to make civilians carry a weapon? I plan on training every dwarf in my fortress up to Adequate or Competent in at least one of Wrestler/Striker/Kicker, but I'd like to get them the same in Swordsman if they will, in fact, keep themselves armed.