Kikou Shoujo Tai Girls Force

Mankind is attacked by aggressors from outer space. Through the godlike devotion of the female emperor, the already desperate human race gains the courage to squeeze the last strength. The research of revolutionary weapons allows to revert the situation. The invaders retreat leaving their destructive weapons all over the universe. This is a story about a military academy where future protectors of the galaxy are being brought up.

[From vndbreview]