I dont know much about this field but what I know is that it is probably going to be hard to find a job in military and they hire nationals. A more realistic option for you would be working for a security company but then a lot of them get cheap labour from other countries... If you are native speaker you can teach English as your fiancee does... alternatively look for on-line postings and look on-line for security firms... but again.. it is going to be very hard.