Interesting read. Digging in and fortifying positions is very much still a crucial part of war. For example, in the current Russo-Ukrainian war, structures such as trenches, bunkers, basements, towers, buildings etc. are crucial for holding onto terrain. Also obstacle-like structures such as concertina wire, anti-tank ditches, dragon's teeth, minefields, czech-hedgehogs, etc. are all over the place. Wherever soldiers appear, they basically dig in and start fortifying, constructing structures both for their own protection as well as for obstructing enemy movement. An interesting recent development are kilometers-long anti-drone tunnels along key logistical routes, meant mostly for stopping rotary FPV drones that are trying to intercept logistics

> kilometers-long anti-drone tunnels along key logistical routes, meant mostly for stopping rotary FPV drones that are trying to intercept logistics

Where they put nets over the road for camoflage or physically catching the drones, right?

I couldn't find a good picture and for a second I thought you meant an earthen tunnel.

This doctrine is changing fast in that conflict. Any enemy structure sticking out is a prime target for drones, and there around 10,000 drones used daily and this number keeps rising continuously, often one-way FPV kamikaze drones. Anything that sticks out is bombarded into oblivion, the tactic now is more akin to hiding or blending with surroundings.

Once they figure out cheap way for semi-autonomous swarms (as in 1 guy piloting say 50 drones, mix of bombers, kamikadze ones and possibly ones carrying some AA rockets) skies will be full of little deadly plastic birds and fortified positions on the battle line will be fully thing of the past.