Chinese Students in Japan: Revolutionaries

Today Japan is the host country of the second largest group of Chinese students abroad, second to the US. Japan hosted the largest number of Chinese students abroad between the late 19th and early 20th centuries. But Japan used to a student of China. How did it become a teacher of China? Some of the Chinese students, either funded by the imperial Qing government or by themselves, became the major force of overthrowing the Qing and China's imperial system. Why?