how can you see if someone really is in the army?

[indef]

if i had to find out i would ask a series of army related questions in person or over the phone. there are a number of things that basic training teaches every soldier and they should know by heart. reason i say over the phone or in person is so they have to respond right then and there so if there is any undue pause or apprehension in his/her reply then you'd know they are full of it.

i would ask basic questions like...

sing me the army song.
explain to me what standard weapons the army issues to soldiers.
tell me the soldiers creed.
...etc.

of course, if they are a veteran then they might know all of this. if you want to take it further you could ask for a copy of their current ERB (enlisted record brief) or ORB (officer record brief). i would also ask outright for phone numbers of their superiors in command to obtain some authenticity.

now... if they can pull all this off and still be fitting of a genuine imposter i would notify the closest army base CID (criminal investigation command) or perhaps the closest FBI field office so that this individual can be dealt with immediately.