Kendo Tanaka was born in 1856. Son of Yiiko Tanaka, a physician of Kumamoto.
Kendo Tanaka forsook his family profession for politics. Influenced by his loyalist associates he enrolled in the Kumamoto army during the Seinan Affair (revolt of Takamori Saigo) (1877) and as a consequence was imprisoned for five years. When he came out of jail, he organized the Hawaii Colonization Company with Keijiro Inoue and others and later became a member of the Seiyukai Party.
After his release he advocated liberalism, and joined the editorial staff of the Jiyu Shimbun (1881). Was again imprisoned (1895) for his complicity in a plot against the Korean Royal family.