home visits

I will preface this by saying that I am completely military illiterate, sorry if I'm asking a stupid question. I have been sending messages back and forth with a gentleman who claims to be a sergeant in the army stationed in Kandahar, Afghanistan. We have not met yet and I have started to question whether or not I am being scammed. Firstly, to be able to speak to me on the phone I have been asked to pay $100.00 to TST Satellite and they will connect us. I have paid the money but there is no connection yet. It has only been a couple of days and I will try to be patient. But there is something said to me today that makes me suspect that I am being taken advantage of or perhaps someone is trying to defraud me of money. So, I need to ask a couple of questions so I can be assured that he is telling me the truth. He states that since he has been there longer than 6 months there is an offer where he could come to the states for a 2 week limited visit over Christmas if I send a letter and request him to come to the states to be with his fiance and family for Christmas. He states that $520.00 has to be paid and will be refundable when he comes back in 2 weeks. That it is insurance money to assure that he is coming to a safe place and will be returning at the end of 2 weeks. He says he will pay me back out of his bank once he gets here to the states. When I told him I could not afford it he kept assuring me he would pay me as soon as he gets here. I have only known him for a short while. I have grown to care for him and he states he is falling for me, but this has thrown up a red flag. I need to know if this "insurance" payment is legitimate.
Is it the practice of the army to make us pay a $520.00 insurance payment for a sergeant who has been there over 6 months to be able to come to the states for a 2 week span over Christmas. He said it was a special offer for officers that have been there for longer than 6 months. Is he telling me the truth or is this a scam to get my money? I told him I could not afford it, and I do not intend to pay it, but I hate questioning his integrity in my head and so I need to know if he was telling me the truth about the money needing to be paid in order for him to come to the states for a 2 week maximum over Christmas. And then, it would be refunded when he returns safe and sound. Thank you for any information you can give me.