Back when I was in JROTC, I had an instructor (a retired colonel) tell a story about how he’d coordinate training exercises (mostly civilian evacuations, defense preparedness, etc.) They’d set up two teams: red, the attackers, and blue, the defenders. They’d brief the red team in advance: locations of installation bunkers, battle stations, etc. but leave the blue team completely in the dark. Blue team goes to bed, thinking there’s just some more training in a few hours, then BOOM, the Big Voice comes on, incoming chemical attack. Everyone puts on a gas mask and make a mad dash to the bunkers. Some guys pretending to be on the blue team stay up top to “defend the base”, but are actually putting on moulage (the fake wounds in this video). Then they start raining down dummy shells that explode midair, and the bunkers start to shake violently, scaring the pants of everybody inside. The moment they scramble out of the bunker, all they see is what they think is absolute carnage. Bodies strewn about, gun emplacements destroyed (simply swapped out in a matter of an hour), just the worst case scenario. They then make a run for the planes to put up more defenses. That’s when they’re stopped, and all the “dead” and “wounded” get up, and the colonel debriefs them. Helped those guys become desensitized to all the gore.