"Although Mormon military action was generally initiated in response to reports of violence, the Mormons tended to overreact and in some instances retaliated against innocent citizens. Their perception of themselves as the chosen people, their absolute confidence in their leaders, and their determination not to be driven out led Mormon soldiers to commit numerous crimes. The Mormons had many friends among the Missourians, but their military operations undercut their support in the non-Mormon community" (The 1838 Mormon War in Missouri, p.4).
I have to wonder why a faith needs a military, why they partake of "military operations" if they are not intending to take over another's land, to seize power and control, for that is a military does. If it is for defense, well that's the government's job.
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I would have to look it up to find which settlements this is true for, The town militia was state sponsored with the town leaders at its head, like the many other towns around.
Since as the author said, the LDS gathered together, that made the town militia made up of the citizens of the town.