Where was it posted that WWIIi will be fought in Underground Cities?

Have watched a bunch of documentaries that the Nazis were incredible Tunnel Builders. They have built tunnels all over the world.

Exploring the Secret Nazi Tunnels Under a German Vacation Town

https://www.atlasobscura.com/articles/exploring-the-secret-nazi-tunnels-under-a-german-vacation-town

DEEP IN THE MOUNTAINS OF Bavaria is a concrete doorway set into the side of the mountain. Even in the height of summer, the thick steel door is cool to the touch, and drips with condensation. From the edges of the door frame comes a chilling cold breeze. It isn’t marked on any tourists guide maps, as the government would prefer that you had no idea that it exists.

Behind the steel door lies the underground secret bunker complex of Adolf Hitler. 

Now hearing that Ukraine has more tunnels than anywhere on Earth?

Going underground: Ukraine's subterranean fighters highlight the …

https://theconversation.com/going-underground-ukraines-subterranean-fighters-highlight-the-benefit-and-long-history-of-tunnels-in-warfare-181454

Latest And We Know makes a bold claim that there are tunnels that stretch to Israel

https://rumble.com/v2i7wt0-4.14.23-news-media.-leakerrestrict-act-controlledmsm-people-still-love-trum.html

Bottom line Nazis are incredible Tunnel Builders and They have Proven History in Ukraine and all over the World…