If you want society to be more vulnerable to military action, then the biggest innovation is health care. Improved health care is what allowed nations to create and maintain larger military forces. Through out history, disease and malnourished caused more death by a large margin than actually violence in combat, and many war campaign stopped suddenly because one or both sides became unable to continue.
I think they mean communicable diseases, not combat injuries. For example, around 2/3rds of the military deaths in the American civil war were from disease, not combat. I don’t think much of the medical advances that prevent that came from combat medicine.
Right, those are relatively minor improvements compared to soldiers no longer dying en masse from typhoid, smallpox, measles, etc. Good improvements to be sure, but not quite as significant.
