For the hundredth fucking time… THIS IS A COMBAT PATCH, as it is on the Right Shoulder, not their Current Unit Patch which is on the Left Shoulder..
In the US Army including Resv and National Guard:
The Unit (Patch) that a Soldier is Currently Assigned to would be on their LEFT Shoulder.
A Combat Patch goes on the RIGHT Shoulder under the US Flag Patch.
No matter what unit a soldier is assigned too, their Combat Patch stays with them, and the only way they would wear a different Combat Patch is if they we (war/combat) deployed with more than one unit.
For Example: Pretend that is a Picture of me, you would see the unit I went into combat (War) with, 3rd Armor Div. and that would not mean 3rd AD is in D.C., you would have to see what Patch is on my LEFT shoulder.
For further Sauce, please refer to AR 670-1
https://history.army.mil/html/forcestruc/docs/AR670-1.pdf
Read here:
Sauce is AR 670-1, Any Current AD US Army, Resv, ANG, or Veteran.
As for the other Branches of the Military ask them, their Uniform Regs are different.