Assume a subterranean civilization exists with technology roughly on par with the modern era. With changes due to lack of certain environmental factors being likely due to the vastly different environment. Assuming tunnels can be bored through the earth creating new routes to fit for instance trains and while keeping in mind limitations due to space.

My reasoning is that in a subterranean environment infantry would be the easiest unit to move around in tunnels and caves. Able to negotiate narrow passages, inclines,small drops,cross rivers,move along ledges,climb and still use available cover. Mecha/power armour small enough would be able to do many of those functions and augment troop power as force multipliers. Where a tank could not fit a small mecha or power armoured unit could quite easily. Not to say a tank of sorts could not be achieved with armoured carts on train tracks that also have treads in larger tunnels and caverns used as main thoroughfare.

However a squad of power armour units is much cheaper than said tank and can go where they cannot. As could smaller mecha units,not being limited to main tunnels but also able to go along side routes too narrow for them.

So my question is: would small mecha/power armour (small being 7-9ft tall being the norm; 12 ft tall being the max) be ideal for fighting in underground conditions?

  • $\begingroup$ I very much appreciate both the answers given to this question. Especially as the second regarding the use of child soldiers helps with issues of the first. Both give me alot of ideas to work with. So thank you. $\endgroup$
    – Obelisk
    Commented Mar 5, 2019 at 1:40

2 Answers 2


Depending on how wide how wide these smaller side tunnels are, I would imagine even the power armour units would be too large to effectively fight in these environments. Assuming that the side tunnels are bored out purposely for humans to pass through, the ceiling is probably going to be 7 or 8 feet high at best, meaning the power armour units are not going to be able to stand upright. Again, the width of these tunnels are probably suited such that people can pass 2-3 abreast. Considering that the power armour units are going to be significantly wider than the average human, plus their weapons (which I imagine are going to be quite a bit larger than the average infrantry weapon) and miscallaneous peices of kit such as radios, food, water, medical supplies, explosives etc, it's unlikely the power armour units would be able to even turn around in these tunnels easily, let alone fight.

Having a mech fight in the side tunnels is probably going to be like how the tunnel rats had to fight in Vietnam. (Another real world example of people trying to navigate confined spaces with quite alot of cave diving- getting your kit stuck on rocks in these tight spaces can be a death sentence). Imagine a small team of mechs inside one of these passages and for some reason they need to quickly fall back- likely their only option would be to shuffly backwards until they get to an opening where they have the room to turn around.

This is in addition to the lack of fine motor control mechs will have, so trying to navigate particularly narrow cave is going to be a nightmare for those troops.

Power armour troops would probably adopt similar tactics to the US in Afghanistan (instead of clearing out a cave, just use explosives to collapse all the entrances and exits, and go on your merry way while the men inside struggle to dig themselves out).

Your average squad of infantry, armed with a carbines and shotguns, would likely be much better and fighting in these confined spaces, especially considering that if the mechs can't follow them, enemy infantry will flee in to them whenever they are outgunned.

Edited based on comment:

Provided that the power armour troops stay within those car sized tunnels, then I imagine they probably would be well suited. They'd be a big target, and probably slower to react in close quarters than light infantry, but given that much of it will be fighting in low light environments due to smoke and debris from hand grenades, gunfire, damaged lights etc, the more sophisticated optics that I imagine they'd have in their helmets would be very useful- though on the other hand I imagine they'd have significantly narrower field of vision through their helmets, so they'd rely on light infantry for support in close quarters.

Also, considering the amount of richocets from shrapnel and bullets hitting the sides of the tunnels (04:00 onwards in this FBI video is very informative on this), as well as the amount of direct fire directed at them fighting in narrow chokepoints, having your point man as a walking shield would definitely improve the life expectancy of any light infantry following.

Depending on the amount of armoured troops that this military has, they may struggle to field enough power armour troops if there are a lot of tunnels to cover (and the power armour troops would probably be overfatigued from constant deployments in any longer term wars), though they'd definitely be a valuable resource.

  • $\begingroup$ Thanks for the quick feedback. I'd say side tunnels on average would probably be big enough for a car to pass through with a small (maybe a foot, being generous) of wiggle room on either side. The main reason is that those passages are still fairly well travelled and opening them a bit would allow greater ease of movement. And indeed infantry are going to be key;especially in a conflict most vehicles can never reach. The only big issue to explosives deep underground is well..... Bad things can happen very easily. Still a valid tactic though for sealing off areas though. $\endgroup$
    – Obelisk
    Commented Feb 26, 2019 at 9:51
  • $\begingroup$ In that case, the power armour troops would definitely be a force multiplier- updated my answer to add additional info $\endgroup$
    – Jack
    Commented Feb 26, 2019 at 10:26

Really small mecha: child soldiers.

I like where you are going with this underground mech idea. But take it one step further. Tunnels bored for worker access / transit will be cramped for an individual in power armor. But not if that individual is 4 feet tall.

Your Mole Corps is comprised of prepubescent soldiers between ages 8 and 11, boys and girls both. Child soldiers are not a new thing but usually are discussed in the context of children being enslaved / coopted by conventional troops.

The Mole Corps arises out of necessity / desperation. It will make interesting writing contrasting the physical abilities of a 10 year old (flexibility, low strength, low caloric reserves, emotional immaturity but without sex hormones. Fearlessness / fearfulness) in the context of technologic augmentation.

  • $\begingroup$ Oooh shiny. This is a new angle on it. I like this idea,it shall find a place within the web to be spun. $\endgroup$
    – Obelisk
    Commented Feb 27, 2019 at 1:30

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