Ukraine

At the very least, you're not losing a crew every time a vehicle like this gets destroyed. Seems logical to pursue when you need every experienced operator you can get

because in those two previously mentioned environments, you can move in all 6 dimensions and it's the same thing, a fluid.

terrestrial is the interface between a fluid and a solid surface. Solid surfaces are super tricky.

I want to see mobile armor mechs with duck feet for the mud season.

Not necessarily technological "advance" but technological "was that really necessary?".

Russia will veto anything the UN tries to do.