I tend to agree with you. I was in the military with a high clearance and knew nothing of the tunnel systems outside those local to specific bases and used for nuclear fallout/protection, etc. (unclassified info)

The only way this fits, in my mind, is if we’re talking about a completely separate society, one speaking a different language.

With that also being said, an interconnected tunnel system for the transport of personnel and equipment during war has incredibly obvious logistical value - and has been done by other countries and to assume the us wouldn’t seems foolish.

The fact that these systems are being used for nefarious goals is what is so disturbing.