Re: officers are called 'sir'
When writting letters if you don't know who will read it, many will start it :-
Dear Sir or Madam
If the use of Sir is not followed by a name, it is simply a courteous way to address someone.
On the continent of wild endeavour in the mountains of solace and solitude there stood the citadel of the time lords, the oldest and most mighty race in the universe looking down on the galaxies below sworn never to interfere only to watch.