Hey, this is quite a bit late, but for future reference:
Here's how I, personally, go about cadence writing. My line likes ghetto R&B-type cadences. So, with that, I like to base the cadence off of a bass drum groove, and go from there.
Cadences don't always have to be structured, but depending on how talented your line is, you might just have to go with simple phrasing and rhythms (besides, this will make it easier for the rest of the band to march to, since that's the main purpose of Cadences usually).
So, a relatively simple structure would be four-measure phrases with fill measures on every 4th measure. Just like a drum-set groove. And some fill measures can be solos for snares, tenors, or basses.
I won't go into more detail about that with what I do, because what I do might not necessarily be what you're looking for since you originally were saying you wanted military based.
And with that aspect, everybody else that has responded, covered the military idea with expertise. So, I just wanted to give my hay-penny advice, after only a few years of writing cadences for my drumline. And it does help to know what your line likes, so that it's fun for everybody to play. I've learned that, for sure.
Happy writing! (Beware: it gets addicting.)
