It's the echoing screams of pure agony that get to Radar most.
"Can't you do anything, sir?"
Hawkeye doesn't answer, motioning for a sedative. Readying the needle, he ignores the growing yells, ignores the wince on Radar's face, ignores the crushing sense of defeat.
"Sir, is that --"
"It'll relieve the pain." He hesitates. "That's all we can do at this point."
Radar merely nods. Neither man can bear to admit they have lost this battle, that another man has been sacrificed for the greater good. A good they can no longer remember.
Eventually, the screams stop on their own.