If it's just a disposable military...
a) Give all your
victims trainees a custom profession so you can find them easily. "Fodder" is a good one to use.
b) In the (m)ilitary screen, (c)reate your first squad (or, if you've got a squad, create a squad appointed by the (l)eader), assign it no uniform, then select your chosen dwarves for each position until either the squad is full or you run out of disposable dwarves. (Normally, smaller squads are better for training, but since this is just throwing dwarves at something, cramming in as many as possible works too)
c) Exit the military screen, then go to the (s)quads menu, select your new squad by letter, then either order them to (m)ove or attac(k) as required.
d) Queue up 10 coffins at the Mason's workshop, or if you have no stone, 10 caskets at the Carpenter's.
As to burrows;
a) Define a burro(w) covering the area you want your dwarves to
stay inside. Call it something identifable, like "EMERGENCY" or similar.
b) In the (m)ilitary screen, go into the (a)lerts tab.
Here you can set a Civilian Alert, and define which burrows your Civilians will be restricted to once set to that alert. Normally it's enough to have one burrow covering 'safe' areas, assign that to your Active/Training alert, and then switch the Civilian alert using this screen when hostiles appear. (Be warned that although
most dwarves will respect this, sometimes you'll get one or two who won't - a Conduct Meeting job for example overrides this, so make sure your mayoral offices are located somewhere suitable!)
That should sort out your excess dwarf problems, at least - if you want a more detailed overview, Girlinhat has recently done a wonderful tutorial on military usage (edit:
found here), plus the wiki has various articles covering the military system.