A high ranking samurai from Tosa, Itagaki was responsible for reorganizing Tosa's forces prior to the outbreak of the Boshin War where he played a major role in leading the campaigns against the Tokugawa forces. After the Restoration, he played key roles in both the Tosa and national governments. He resigned from the Meiji government in 1873 in protest of the decision not to go to war with Korea, and became a prominent leader of the Freedom and People's Rights Movement (Jiyû minken undô), signing early the following year (17 Jan 1874) a Petition for the Establishment of a Popularly Elected Assembly, submitted to the government; the memorial was also signed by the likes of Soejima Taneomi, Gotô Shôjirô, Etô Shinpei, and Yuri Kimimasa. Itagaki subsequently returned to government and held various cabinet posts until his retirement in 1900.
A prominent Taishô liberal, he pushed for a number of liberal policies, including extending the full rights and privileges of citizenship to Taiwanese and Koreans, a proposal which was proposed in 1914 but ultimately quashed after coming up against considerable opposition.
- Hillsborough, Romulus. RYOMA- Life of a Renaissance Samurai. Ridgeback Press, 1999
- Jansen, Marius B. Sakamoto Ryoma and the Meiji Restoration. Columbia University Press, 1994.
- David Lu, Japan: A Documentary History, ME Sharpe (1997), 326-329.
- "Liberal Party founder Itagaki favored Louis Vuitton goods, 1883 purchase record shows," Japan Times, 13 July 2017.
- Mark Peattie, "Japanese Attitudes toward Colonialism, 1895-1945," in Peattie and Ramon Myers (eds.), The Japanese Colonial Empire, 1895-1945, Princeton University Press (1984), 103.