I wouldn't necessarily think so. Maybe infantry men, marines and paras, but there are a lot desk jobs in the military.
I worked in an office job with the australian army, and they were very sedentary. They got Wednesday afternoons off for sport, so they could stay fit, but the Staff Sergeant I worked with went bowling, and most of the rest of them played golf. Noticeable exception was Wonder W.O. (formerly known as super sergeant), who did 500km+ ultra marathons.) They had a fitness test each year, but it wasn't that onerous.
You could ace
these tests, and not be nearly ready for a half ironman.