Akamaru Monogatari (2009)

Movie tells a story about Japanese history, beginning with wars in 1600 AD. Starting with Japanese civil wars and the falling of Shogunate, after which comes the period of Japanese attacks on Russia and China, through the period of Great War and World War II. To this point the movie is made like a documentary, but after that it becomes a fiction. Japan prospers for the greater good of the mankind to the point when Earth is attacked by an alien force. Japan, trained for war, is the only one who can stand in the way of this much advanced war civilization. This is the time when they activate their robots, to fight against alien threat.