Campfires
Can be kept burning unattended by stacking a crosshatch of the correct mix of dry & green logs lit at the top. Leave a small gap between. Under a canopy.
Fortification, Consealment & Decoy
Surround your target with nodes of thick concrete with a hole to jump into, between them hide nodes of concealment to rush out. They will try to send several together if they fail. Paratroopers might find nothing but tents & firewood if they take your position, give it to them. Wait for the chopper to lift that & them. Sprinkle compost over your secret hatch & lay turf. Cut around in later using a metal detector to find the gap. Same for air, don't extend a pipe, rod from within.
Restore fortification
How Quickly can skilled men dig a hole to jump into & place concrete blocks around? Shallow bury them hooks outside off site. Cover a small digger. Scrape the ground within & ground zero is cool again. Keep three of everything if you are serious about holding the site.
Under construction
A narrow trench under buildings will withstand heat & blast blowing it all away. Crawl space, 20mt.