If you liked the Muv-Luv Alternative: Total Eclipse anime, the Anime-Planet community thinks you'd like:
In the year 1945, the most terrible creatures in existence visited the earth: bug-like entities soon to be known as Phantom Beasts. In that time of peril, mankind joined together to expel the threat, only to find that conventional weapons were useless and further damaged the earth. It is now 1999, and the student-wide draft has changed the lives of thousands of teenagers across Japan. While unwillingly fighting in an endless war that started before their births, one group of friends will experience the tragedy of death and the bittersweet joy of love as they struggle to survive.
These animes really resemble each other in many aspects. There's fictional past, where aliens have overtaken earth and people lost most of their countries, but they're still fighting to get it all back by military force in form of mechas. Even the plot is set in military environment and main subject is character's thinking. Because Muv-Luv is still ongoing, I can't say, if in case of Muv-Luv will be any romance like in Gunparade March, it doesn't seem this way, but it's not impossible.
In the not-too-distant future, Earth was attacked by mysterious beings and before long over a third of the world's population was destroyed. Even after bringing to bear its full, united military strength, humanity was unable to repel the assailants and forced into using weapons of mass destruction. This was successful, but the war and its conclusion resulted in the deaths of a crushing percentage of all fighting-aged males, and Antarctica being melted, causing much of the Earth's land to sink underwater. Years later, three young girls - Otoha, a headstrong country girl; Karen, a technical genius; and the highly-disciplined and strong-willed Eika - are being trained to pilot Sonic Divers, weapons being developed lest humanity be caught off-guard once again.