@dsuke
But from your own link:
The largest mining operations were conducted in the Battle of Messines, where specialist Royal Engineer tunnelling companies placed 22 mines under German lines. 19 were eventually exploded, killing about 10,000 German soldiers. Underground attacks especially broke the morale of the enemy if he was surprised in his secure positions
Ie., it actually worked. The discussion here was about whether a mining operation this massive under the Empire's own lines which they then lured the Francois over should realistically have been discovered at this stage of the war. I'm arguing that nothing of that scale had yet been done, not that it was never done at all in history. In the story itself they point out it was an old tactic, reapplied for the modern era. But that doesn't mean it couldn't still be a surprise, and certainly not when done as a strategic move. The Battle of Messines itself was in 1917, so 3 years in and almost at the end of WW1.
I don't think it actually goes into specifically how they dug those mine tunnels, but it can be inferred that they were able to in part because they could be a lot noiser and less careful about it then normal because they controlled the above-ground. If the Francois had realized it was a trap, they wouldn't have moved forward that way in the first place, and surprise and speed were baked into the plan. At this stage of things Tanya's introduction of the total war concept and fighting for resources vs territory was pretty revolutionary. I don't think the setup here was badly done, or that the Francois were wrong to have not somehow dug down deeply as they advanced.
So I'm just arguing that the Francois were not stupid, careless, fought badly, or anything like that. They worked hard and had smart people on their side. But the Empire was better at this 1v1, they were outmaneuvered in tech, strategy and intelligence at the strategic scale is all. And other countries do adapt and learn lessons too, and the Empire makes major missteps and loses tons of valuable people, grinding down completely towards the end.