After the Tokugawa were overthrown, Yamagata and Saigō Tsugumichi traveled abroad in 1869. They were sent to research the military systems of western countries. Yamagata was impressed with the Prussian military. After a year Yamagata returned and reported directly to Emperor Meiji in Tokyo. He was made "Assistant Vice Minister of Military Affairs". He used the military theories of Carl von Clausewitz and Prussian war games to change Japan's army. He became War Minister in 1873. He modernized the Imperial Japanese Army and made it like the Prussian army. He started military conscription in 1873.