Yeah, I think the overall conditions of the "battle" have to be taken into account.
Need to factor in a War in extreme cold. If you get a chance read ...
Breakout: The Chosin Reservoir. I had actually put that one in my original post and then deleted it.
Intensity of battle over time would also factor in. Chosin and the Battle of the Bulge were both fought in painful cold. Iwo Jima was intense,non-stop fighting for weeks, as was Okinawa and many other Pacific battles, many fought in extreme heat.
To be honest, the German Army in the 20th Century could probably hold the title for having fought in the worst battles - and after brief initial victories they were always falling back which is a lot tougher to endure psychologically.
