Which preposition to use with switchmen

behind Occurrences 1%

It means doing what you are told to do as well as it possibly can be done, no matter how small it is nor who is looking ona sense of duty which makes every switchman behind the lines act as if he were Von Hindenburg.

on Occurrences 1%

The railway management places a switchman on duty at this delicate post.

Which preposition to use with  switchmen