On 23 December 1871, he accompanied the Iwakura Mission on its round-the-world voyage to the United States and Europe, and was especially interested in Western educational systems and politics. On his return to Japan on 13 September 1873, he would become a strong advocate of the establishment of constitutional government. Realizing that Japan was not in any position to challenge the Western powers in its present state, he also returned to Japan just in time to prevent an invasion of Korea ("Seikanron").