After returning from study in Britain, he was earnestly engaged in overthrowing the Tokugawa shogunate and contributed to establishing the New Government. In 1871 he made an inspection tour of Europe and America as vice envoy of the Iwakura mission. He was appointed to important posts such as the first Prime Minister and Privy Council Chairperson and made an effort to establish the Constitution. He formed the Cabinet four times and was nominated as the senior statesman.