Lots of non-infantry folks earned CIBs in Nam while serving with ground combat forces. And everyone, regardless of branch who serves in a combat zone, earns the right to wear a combat patch.
And proud of it! Luckily I never had to prove my manhood by jumping out of a plane - that and all the weapon systems I served on couldn't be air dropped....
Back in the 70's, I had a 2LT friend that spent 3 months with the French Foreign Legion on an exchange officer bit. They still had these and other WWII left overs as primary equipment. No parts except what they made by hand.