[int_19h]

On the contrary, a fleet of cheap drones is what renders walls (and more broadly barricades) useful again. They don't have to stop the advance - they just have to slow it down so that the advancing units can get hammered by drones and by drone-guided artillery. Drones also make it nigh impossible to do any kind of surprise attack, which in turn means that fortifications can be made where they are actually needed, and not like e.g. the infamous Maginot line.

[kergonath]

The Maginot line gets ridiculed often enough, but it did its job: it forced the Germans to find another way. It’s too bad the Ardennes were much more porous than expected and the fortifications did not extend all the way to Dukirk, but without fortifications at all it’s pretty much certain that the Wehrmacht should have gone straight through the plains of Lorraine and Champagne.