Gate: Jieitai Kano Chi nite, Kaku Tatakaeri Flame Dragon (GATE 自衛隊 彼の地にて、斯く戦えり 炎龍編)
One day, after Tokyo was attacked by an army of monsters, the Japanese Government sends their troops through the magical gate which the enemy army came through.
On the other side the soldiers find themselves in a Roman-styled fantasy world. Their task: open peace negotiations.
A high quality anime with magic, dragons and elves. A must-see!