"Jim, most of us here, including you, are too young to remember when "friendly fire" entered the language."
Must have missed it, I genuinely never heard it prior to the Vietnam war
It apparently originated in World War One, but was never accepted as a term until WW2   
Must be my naive opinion that killing anybody is distinctly 'unfriendly'

I assume I'm ok with 'Collateral damage' (May 1961 - Vietnam) - and 'Special rendition' (2005, when the US started sending terrorist suspects to countries notorious for their use of torture to be 'questioned - though there were rumours of it four years earlier)
Jim