King2Hearts is sort of military and romance. I loved it so much. It stars Ha Ji Won and Lee Seung Gi. It aired in 2012 and has 20 episodes. It's underrated and no one talks about it but it's cast became big stars in the future. The female leads character is so epic, she's really strong and such a sparkplug.
There are also more obvious military and romance dramas like Descendants Of The Sun and Crash Landing On You that you could watch if you haven't. They are both good and very popular dramas.
Also Military Prosecutor Doberman started yesterday but I'm not sure if there will be any romance as it is not listed.