Kudos to you for your service in the military.
This is a user to user help forum only, so no one here knows if Apple has plans to sell the iPhone in South Korea in conjunction with a cellular provider there. The list of countries where the iPhone will be available is expected to grow this year and next, but we won't know until Apple makes an official announcement.
Even if Apple sells the iPhone in South Korea at some point, doubtful you will be able to use your iPhone there with a provider that Apple makes a deal with, which was sold in the U.S. as carrier locked with at&t only.