I's never heard of friendly fire until the US began killing their own in Vietnam and later Afghanistan
I have little doubt it was invented to sanitize what was happening
It's simply not good enough to used wods like 'complicated' when the real cause is that weapons have been developed to create fear rather than take out opposing troops (Hiroshima and Nagasaki are pretty good examples of that)
You might as well add 'special rendition' to the list - torture has always been torture, whatever you call it
When I was comin' up, it was a war crime - not musch sighn of 'prosocutin of that nowadays - or perhaps there's a new word for that too !
Jim