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.
Bronetransporter
In the MILITARY, the term "Oscar Mike", is used to say "On the move". Oscar standing for O, Mike standing for M. The use of "the" is taken out totally. So, Oscar Mike. :)
To be forced into service
It means to be armed
secured area
Extended combat training
Died While Missing
north Atlantic treaty organization
It is "Basic Active Service Date"
member of a State national Guard Unit
If you're talking about military terms, it stands for Letter Of Notification