ISIS digs tunnels hundreds of meters underground so no need to go back to vietwar.
Tunnels are not much use today, but Gaza is different because the tunnels are below civilian buildings so Israel can't use the special tunnel busters that Americans supply them as it will cause the entire city blocks to collapse. These tunnel ordnances can suck up the air in the tunnels, creating a vacuum and the entire tunnel system will collapse.
taster for tunnel in modern context.
his tunnel experience is with kurdish groups against turks
and friendly casualties that occur during human tunnel clearing ops logically have low survival rates, considering how hard it is to extricate them out in time
if no major tunnel ops planning to deal with, i think tanks already rolled into gaza last week.
drones cannot rely on GPS underground, they will need inertial navigation. i reckon they are delaying to rush out prototypes to use for this, be it with LIDAR mapping or as expendables to fly ahead to scout, bait fire and trigger/detect traps
like this good ol drone scene