OMG, at 2:04, is that film for real, or is it a movie?
The soldier that's down is probably a 2nd lieutenant, still waving his men forward.
Sherman was right about war being all hell, whatever the circumstances, but WW1 was probably the most hellish, though they did have trench warfare during the last few months of the Civil War, and amputation of shattered limbs without anesthesia was common in that war.