Radar was developed before WW2. It was just really expensive, so analogue systems (eg, mk1 human eyeball, and this monstrosity) were used to supplement.

Different but the greeks when besieged were known to drive stakes of brass with a thing brass plate above ground attatched to it at intervals, then they could see the vibrations from anyone tunneling under, what do they call it, sapping, they dig under, then burn the supports and collapse a section of wall to breach the city.

One incident the greeks made a chemical weapon out of chicken feathers and chicken shit and charcoal and lit it and threw it down there after they counter tunneled into them after seeing their vibrations.

Given the ubiquity of explosive drones specifically I feel like we need that calendar cartoon with March 2026 being torn off to reveal July 1864

Not sure how much is militariaganda, but there was a dude slinging one of these around during a couple of big diplomatic events in the past couple of years, so probably partially effective at the very least.

Oh and there's also whatever aircraft mounted variant that the americans used when they invaded venezuela, the one that made Maduro's guards "bleed from the eyes, ears and nose", while describing feeling like someone had parked a car on their head.