I was reading something a while ago that claimed a group of British soldiers were swimming in a river because they were given a few days free time, and a group of other British soldiers came along drunk and started throwing grenades into the water with them and I think it said taking pot shots with rifles. Is this sort of thing documented in reliable sources or is it likely just made up?
I know of documented cases from Vietnam and the Korean conflict regarding friendly fire and fragging but in terms of documented WW2 incidents of DELIBERATE friendly fire I don’t think it was as openly talked about in that era and I haven’t come across much documentation regarding this with the allied forces.
I do know of several cases in the African theatre where Italian and German troops exchanged shots in anger. While Mussolini and Hitler played buddy buddy, often the common Italian soldier did not have any affection for their German brethren (many of the Italians still remembered the Germans as their enemy from the Great War) the German open attitudes of superiority towards their Italian counterparts did not help this atmosphere.
A quick example I can cite is in the Siege of Tobruk, the Germans decided to break out and requisitioned any available Italian trucks to help with this movement, an Italian sentry attempted to stop them and was shot resulting in a running gun battle down the street between the pissed off italians and the Germans pulling out in the Italians vehicles.
There’s also a few examples of Italian units who refused to surrender or did not surrender quickly enough to the Germans upon the Italian armistice and were put down brutally - Operation Ache (though technically they were no longer allies at this point)
A story from this that always stuck with me was that of General Ferrante Gonzaga, the commandant of the Italian 222 Coastal division who when presented with surrender terms told the Germans “A Gonzaga never surrenders his weapon” while rising from his desk and attempting to draw his pistol. He was shot down and killed but the German after action report spoke well of him as he ‘had died a soldiers death’
One other incident in the war that might fit your question , albeit with a slightly different twist - the battle of Castle Itter. Considered one of the strangest battles of the war - it consisted of US troops, some notable French POW’s (former prime ministers and generals - even a tennis star) and the WEHRMACHT fighting together against members of the 17th Waffen SS so an example of German vs German fighting