Can I wear the 2nd Marine Division Combat patch?

Nope. The one and only way a soldier can earn/wear a Marine Corps combat patch is if they are in the Army and attached to a Marine unit. Time spent in a Marine unit while a marine does not count. The uniform reg is pretty clear on that. In fact, you could be a Marine attached to an Army unit. Then you would still not be allowed to wear that Army patch as a combat patch even if you went to the Army. Combat patches can only be earned while a member of the Army.

I was in the Corps, went to the Army Reserves for a few years then came back to active duty in the Corps. You cannot wear a combat patch because you were not in the Army at the time of your service. You can wear your combat action ribbon and all the awards you earned during your service as a Marine. I could wear the Army Service Ribbon if I wanted to, but I would never hear the end of it.

There is a process for the ribbons and medals (I don't know exactly what it is, but I know enough people that have switched services to know that there is one). Most, if not all, will transfer over. DA Pam 670-1, page 229 lists some that don't.

As for the patch, you may be SOL. I looked it up in AR 670-1 (thanks John Hinkle). Here's what it says on page 33.

(2) Personnel who served in a designated area as a civilian or a member of another Service, but were not a member of the U.S. Army during one of the specified periods are not authorized to wear the SSI-FWTS

The AR and Pam also address some badges that might not transfer.

No. I was in the National Guard, and I asked if I could wear my I/3/9 patch. The Marine Corps does not allow you to wear their patch on another uniform. Semper Fi.

no combat patch

most should transfer

yo have to make a choice -- keep wearing the marine CAR or decide to wear a army CAB

first off, thank you for your service.

secondly, and this is my educated guess, but, since you are in a new unit, and new branch of the military (is it army, air national guard, what?), i don't believe you can wear service medals or ribbons since they weren't assigned with your new branch and unit.

can you ask your superior or a counselor or adviser at your base of duty? I'm sure they would have the knowledge to answer those questions.

good luck and stay safe.

Contact Marine Corps Personnel regarding heraldry and medals.

You'll need to give them your SSAN, name, and the time period in question.

Google AR 670-1 and look it up.