Sorry - I didn't catch that. So apparently you received an error on his profile and you're trying to resolve. I'm assuming the error said that the Wounded in Action category is incorrect and you'd like to fix it. Hopefully I'm capturing that correctly.
From what I can tell, the next level down is acceptable. That one is: Category: Wounded in Action, United States of America, Korean War
As Natalie mentioned, if the Categorization Team adds his unit, you can then change it to the Unit category instead, but I think at this time there's no subcategories under Wounded in Action, so this would be the best choice. My guess is that they might add his unit to the Units page, but that would be an additional category to add.