My grandpa faught in WWII, and he talked a LOT about foxholes and slit trenches.
As a child, I couldn't really fathom digging anything deep enough to fit into. My digging experience was in sandboxes or on the beach.
So I asked him "But... How long did it take to dig the holes? Wouldn't it take a long time?"
And he answered "You can dig pretty fast when you're getting shelled" and I feel like there was some kind of wisdom in that exchange that far transcended the immediate subject.