The corpsman strapped his patient onto the litter as the sound of swirling helicopter blades roared from a watchful instructor’s hand-held speaker. Double-checking his IVs were secure, he and a stretcher team hoisted up their casualty and sprinted toward the landing zone amid flying debris from the helo’s rotor wash — in this case, a leafblower.

On this makeshift battlefield in the parking lot of the Army’s Joint Special Operations Medical Training Center, medics had already quelled enemy fire, stopped the bleeding, drawn two bags of blood from teammates for the wounded, and carried him half a football field to a protected position before the…