Well why is it such a surprise? I mean perhaps he was someone who was vigorously exercising and taking care of him.
If you start looking at the Eastern Front in Europe there are seventy year olds that fought as guerillas or during the siege battles.
I think people really were just so much more physically active than what they are today. Now on the flip side there is a wealth of knowledge available today and numerous programs available to join that can help you stay young and active.
Paul Douglas indeed enlisted as a private and went to Paris Island. After basic, they kept him there for a while as a lecturer.
He rose to Captain in 1943, Major sometime in late 1944 and retired as a Lt. Colonel in late 1946.
Amazing guy but it didn’t happen in one year.