I also recall from my basic training an episode that fits here:
I was in the Luftwaffe and had my very first 36 hr exercise in an old IHAWK SAM battery. These things have artificial ridges, about 5 m high.

I was told to build a shallow defensive position on such a ridge; for two persons, with sandbag cover and camouflage. I declared it ready after a while, but the trainer disagreed and I had to add another layer of sandbags.

I looked at it from the OPFOR direction and it stood out very much. The camo was a joke, no matter how much vegetation I applied.

Later that night, I simply left the position (which was easily visible even in quarter moonlight!) and prepared under the cover of darkness a very, very shallow fighting position 10m next to it (an OPFOR NCO, our original platoon leader, had been allowed to inspect our positions in daylight).
That night OPFOR tried to break through 50m to my right side and attempted to suppress/destroy my position. They did merely hit the empty, easily visible sandbag castle. I would have been declared dead in the first second of the attack if I hadn't left it earlier in the night.
I never, ever used a ridgeline or forward slope position again. I even relocated some bushes behind my other positions to avoid a helmet-shaped silhouette in later exercises.


If I - as a 18 y.o. private - was able to figure this out on in advance of my first try, why are there still proponents of main defences on forward slopes and ridgelines?