In WW2, German saboteurs in the USA caught out of uniform, and as spies they were simply executed —quickly and quietly. It also happened many times during the Battle of the Bulge.
“In WW2, German saboteurs in the USA caught out of uniform, and as spies they were simply executed —quickly and quietly.”
It wasn’t quite that simple or quick. Here’s a good recent book on that incident:
http://www.amazon.com/Horseshoe-Curve-Sabotage-Subversion-Railroad/dp/0977980510