I suspect the cheapest option would be cameras mounted on artillery shells. https://www.afcea.org/content/artillery-eyes-provide-sight-ground-forces https://ww

I suspect the cheapest option would be cameras mounted on artillery shells. https://www.afcea.org/content/artillery-eyes-provide-sight-ground-forces https://www.afcea.org/content/artillery-eyes-provide-sight-g... The U S army worked on putting cameras in howitzer shells as far back as the 70’s, so short-ish range (10 miles or so), but cheap by military standards. Though these days a cheap plastic drone might easily be less expensive if mass produced.