I took basic training at Ft. Knox, Kentucky in 1981. During our last forced march, before graduating, one of our Platoon members was falling behind and didn't seem able to finish.
Another recruit and myself grabbed his pack and picked him up under each arm and practically dragged him across the finish. My Drill Instructor, a Vietnam veteran himself, and not one to give out many or if at all compliments, looked at the three of us coming across the finish line, and said, "now you get it".
I sure did, and that 'can do spirit' and never leave a man behind thought process stayed with me till this day.