Even the Army, (My alma mater) has one listed as primary, infantry rifleman. We, even in the ordnance corp, had our weapon at the ready at all times in the combat zone. You could be called at any time to go to an infantry platoon and do grunt duty, fortunately I escaped that dillema, but it was a threat the non-coms and officers always held over your head. Whenever going on a field excursion, you always had your weapon in hand, and yeah, I did experience incoming more than once. The sound of an AK being fired at you is rather terrifying, the noise a round makes going by you is something one never forgets, generally, you hear the round before you hear the gunfire, like zing-pow, sounds like chinese food, eh? Incoming mortar rounds are even more terrifying. I would have made a terrible grunt.
So your basically saying that the Army does NOT send every person into combat operations like the Marines do. Im saying that there is no maybe, you WILL be part of a Platoon and go on long 50 mile hikes up mountains at 10 MPH with a 100 lb pack on, you will spend weeks shooting various weapons and riding in all sorts of vehicles and spending weeks on end sleeping outside in the dirt. You will endure all the combat training/jujitsu/self offense classes and the endless miles of running and hours of PT ( Physical Training). Then after its all over you can go back to your cook position/ Office position/ tech job. No one holds this over your head as some kind of punishment. Most Marines look forward to the brutality of it all.