Ordnance is military equipment. Originally used to just mean artillery and other similar mounted guns, it eventually expanded to include pretty much anything that explodes.
An ordinance is a rule or law passed by a municipal authority.
I keep seeing sentences like this:
“NATO armies don’t have more ordinance in that 300-500 km range because they fully expect air power to deliver ordinance at those distances.”
I just cringe when I read this. I think the coverage here for the Ukrainian conflict is excellent, but confusing these two words is really unfortunate.
Hope this helps!