When you're deploying something to the warzone, there are many unknown unknowns that affect the outcome. Things get predictably attacked and the defense can get

When you're deploying something to the warzone, there are many unknown unknowns that affect the outcome. Things get predictably attacked and the defense can get unpredictably destroyed. Firearms and tactics evolve over time and very few things can really be blamed on the engineer. The rules for PE are also based on evidence of due diligence on known problems rather than absolute liability, because nobody knows everything that could happen, and can't cover all possible failures. You should read up on how tanks are destroyed or stopped in inventive ways in guerilla warfare, such as in the ongoing Ukraine conflict (it's not just failure of maintenance) or in Vietnam war. I also don't understand why you could selectively skip the part about novel chemicals.