It was about the Maisy Battery near the coast NE of Carentan and the fortifications at La Puinte Du Hoc.
The Americans pounded the Du Hoc to bits but when they climbed the cliffs they found that the big guns had gone. They had been moved to the Maisy Battery which no one appeared to know about at the time.
It took then 3 days to find the Maisy Battery. It then disappeared after the war until a researcher going through old documents found it and had it unearthed.
Itís said that the locals never knew about it until it was Dug up
It delayed the American landings and cost lives.
Thatís just the gist of the story.