Thud I didn't quite get why you brought Eastern Front here ... but I recently happened to see a short documentary about how Slovakia guards its very short border (97 km) with Ukraine: they invested into lots of electronic equipment, trained Army and Police members to be "invisible" etc. and it appears to work HOWEVER the intruders are smugglers or armless refugees together with people traffickers (who are armed for the case their clients asked their fee back
and not to shoot it out with a squad like this one:
so you may tell us how Ukraine should guard its border against people who are crossing it to "liberate Ukraine from Kiev Junta"