Rob Pincus lays the groundwork for training for defensive shooting in close quarters with a threat, using a handgun when it is in close proximity to your body. A Personal Defense Network (PDN) original video.
Old-school thinking held that if a tourniquet were used on an extremity wound, the injured person would lose that limb. That has been shown to be incorrect, and tourniquets are now in the first-aid kits of medics on battlefields and streets worldwide.
Rob Pincus discusses zeroing your home defense long gun optic and why the normal rules of The Plausibility Principle are trumped by the efficiency of zeroing your rifle for much further distances than you would most likely be using it.