There is no one in the military, no one named Sargeant Lewis Thomas Buchana, no one from Afghanistan, no one in a government hotel, no one on special assignment, no one going to travel to South Africa, no one needing a leave request, no such thing as "pay for military leave", no money will ever be refunded to you and absolutely nothing legit or real in any of those emails from a scammer. Sorry to say but everything you have been told is a total lie, all completely made up with one reason, to steal your emotions and money.
The next email was from one of the scammer's fake names and free email addresses and has demanded you pay for made-up fees, in cash, and only by Western Union or moneygram.
Western Union and moneygram do not verify anything on the form the sender fills out, not the name, not the street address, not the country, not even the gender of the receiver, it all means absolutely nothing. The clerk will not bother to check ID and will simply hand off your cash to whomever walks in the door with the MTCN# and question/answer. Neither company will tell the sender who picked up the cash, at what store location or even in what country your money walked out the door. Neither company has any kind of refund policy, money sent is money gone forever.
Now that you have responded to a scammer, you are on his 'potential sucker' list, he will try again to separate you from your cash. He will send you more emails from his other free email addresses using another of his fake names with all kinds of stories of great jobs, lottery winnings, millions in the bank and desperate, lonely, sexy singles. He will sell your email address to all his scamming buddies who will also send you dozens of fake emails all with the exact same goal, you sending them your cash via Western Union or moneygram.
You could post up the email address and the emails themselves that the scammer is using, it will help make your post more googlable for other suspicious potential victims to find when looking for information.
Do you know how to check the header of a received email? If not, you could google for information. Being able to read the header to determine the geographic location an email originated from will help you weed out the most obvious scams and scammers. Then delete and block that scammer. Don't bother to tell him that you know he is a scammer, it isn't worth your effort. He has one job in life, convincing victims to send him their hard-earned cash.
Whenever suspicious or just plain curious, google everything, website addresses, names used, companies mentioned, phone numbers given, all email addresses, even sentences from the emails as you might be unpleasantly surprised at what you find already posted online. You can also post/ask here and every scam-warner-anti-fraud-busting site you can find before taking a chance and losing money to a scammer.
If you google "fake Afghanistan scam Western Union", "fraud Western Union military love scam", "fake military leave scam" or something similar you will find hundreds of posts from victims and near-victims of this type of scam.