It's from the phonetic alphabet.
The letter C is spoken as Charlie
In military terms, "Charlie" is often used as a phonetic alphabet code for the letter C. It can also refer to specific military terminology such as the Charlie Company, which is a unit within a larger military organization. Additionally, it is sometimes used as informal slang to refer to the enemy or hostile forces.
Oscar is simply "O" but expressed as part of the phonetic alphabet. For example, Alpha, Bravo, Charlie, Delta, etc.
This is not used in the U.S. military.
Wanna know what Charlie Daniels plays? Are you sure? Ok, well he plays A MEAN FIDDLE!!!!!
Bronetransporter
To be forced into service
It means to be armed
secured area
Died While Missing
Extended combat training
north Atlantic treaty organization
It is "Basic Active Service Date"
member of a State national Guard Unit