A common trope in action films, shooter videogames and whatnot is to have a “Special Forces zipline”. Basically the premise is to allow your SWAT guys or Delta Force commandos to tactically and dramatically egress or ingress into battle.
Am I correct in assuming that there is no real military value in using an inclined high-tension cable strung between two prepared fixed points to assault a position?
Note, this should not be confused with rappelling or fast-roping out of a helicopter.
Yes, the Enemy would attach the bottom end of the line to a minefield.
It makes a useful impromtu system for transport. Look for the story of an East Berlin family that escaped over the wall. In some parts of China, long ziplines made of bamboo are used to cross gorges and ravines. Things transported include people, goods, wagons, live horses and cattle.
I see the usefullness of it, but as far as an actually tactical fight goes, I don’t think there could be much ‘impromptu’ about it. And it would definitely have to be ending somewhere the enemy had no knowledge of, or, as mentioned above, kablooie!!
My old field manual would describe something very akin to a zipline as a fast means of clearing out of a high position after carrying out an ambush in built-up areas. (In cities, you want your anti-armor team high, to get at the thin rooftop armor.) It was definitely mentioned as an alternative option - as in, if you have the time and materials, and there is no better way to extricate, this could conceivably be useful.
Is that the same thing that the mayor of London ended up hanging from during the Olympic opening ceremony?
I can see where a sniper might find it useful. The snipers are usually holed up in a high vantage point to have the best line of sight, but if they are seen they are very vulnerable. If they could set up a zipline and get out of there in a hurry, I could see it as being an advantage for them.
Typically in the movies/games the zipline is set up very quickly by using a grappling gun to secure the line to the endpoint, tying it off at the start, then using it once and forgetting about it later. Either that or something in the environment such as a power line is used.
I don’t think the writers worry too much about getting strategic ziplines placed in the field before the operation.