I grew up near Miramar Naval Air Station in San Diego. Uncounted Marines
trained there, and so did Patton, and our first Commando units , Carlson's
Marine Raiders.
We used to find all kinds of fun stuff. Dad like the case of rifle grease I
carried home, but mom called the cops and wouldn't let me keep a string of
machine gun ammo. Shells were out. A dumb kid or two would blow up every
few years, and they still annually sweep for more shells uncovered by
weather. Most of the ground is now permanently covered by houses. Don't dig
in the yard, kids. I can't imagine what it would have been like if mines
were present.

I have walked many of the WW1 battlefields. There are still some unplowed
areas around Verdun, etc, where the ground is very "hilly", filled with
small trees, and silent. As it should be.
--
Stupendous Man,
Defender of Freedom, Advocate of Liberty