He was born in Kubokawa in Tosa Province, the fourth son of Tani Kagei, a Confucian scholar serving the Tosa domain. Because his three elder brothers died young one after another, he became the heir. Raised by an uncle, he was a restless child, but as he grew he became devoted to study and drew the domain's attention.
He went to Edo and studied under Confucian scholars such as Yasui Sokken and Asaka Gonsai, the Neo-Confucian Shionoya Tōin and Wakayama Futsudō, who taught Yamaga-school military science. After a few years of study he returned to Tosa and became an assistant teaching history at the domain school Chidōkan. Mastering both learning and military science laid the foundation for his later career as a soldier.
On his way back from Edo he met Takechi Hanpeita and leaned toward sonnō jōi ideas. He debated foreign policy with Yoshida Tōyō, who led the domain's government, and is said to have admired his breadth of mind even while opposing him. After Tōyō lost his life, he was taken on with Takechi as an aide to the domain lord and mixed with activists from other domains in Kyoto.
When Takechi Hanpeita lost power and was arrested, Tateki, seen as a comrade sharing his views, was also demoted and spent some time shut up at home. The next year he returned as assistant at the domain school, but his jōi views changed little; he criticized, for instance, the policy of enriching the country and strengthening the army pursued by Gotō Shōjirō, who carried on Tōyō's line.
In Nagasaki he mixed with Gotō Shōjirō and Sakamoto Ryōma, who argued that expelling foreigners was impossible. Seeing Western military power firsthand in Shanghai, he changed his mind and began calling for opening the country and overthrowing the shogunate. At Komatsu Tatewaki's residence in Kyoto, he and Itagaki Taisuke met Saigō Takamori and others of Satsuma and made a secret pact aiming at armed overthrow.
When the Boshin War began with the Battle of Toba–Fushimi, he marched out with Itagaki Taisuke at the head of Tosa troops. At the Battle of Kōshū-Katsunuma he defeated a unit that had grown out of the Shinsengumi, fought in northern Kantō and joined the siege of Aizu's castle. Returning to Tosa in triumph, he received an increased stipend for his war service and was given an important domain post.
After the abolition of domains he served the new government and, after becoming a major general, was made commander of the Kumamoto garrison guarding Kyūshū. He worked to modernize the army by giving his troops French-style training. He later joined the expedition to Taiwan but, dissatisfied with government policy, withdrew to Tosa for a time, and was afterward again appointed commander of the Kumamoto garrison.
In the Satsuma Rebellion he held Kumamoto Castle for more than fifty days against attacks by the Satsuma army led by Saigō Takamori. Just before the fighting a fire broke out in the castle, destroying the keep and more, and the siege was a hard one with food running short. He himself was shot and badly wounded, but relief forces arrived, the siege was lifted, and he contributed greatly to the government army's victory.
For his service in the Satsuma Rebellion he was promoted to lieutenant general and headed the Army Military Academy among other posts. But learning that government and army leaders had ignored the rough handling of the remains of soldiers who died in the Taiwan expedition, he resigned in protest. That year he also opposed a scandalous sale of state property to officials' associates, and with fellow officers submitted a petition calling for a national assembly.
Asked by Itō Hirobumi to reform the education of the nobility, he became head of the Peers' School. He promoted education so that sons of noble families would become a bulwark of the imperial house, and sought to train people who could work fairly in future parliamentary politics. In recognition of this work he was made a viscount under the system established that year.
When the cabinet system began, he became the first Minister of Agriculture and Commerce in the first Itō cabinet and set out on the path of a politician. From the next year he traveled through Europe for over a year, studying conditions in each country. Worried that importing too much Western civilization would weaken the nation through debt, he grew increasingly critical of Japan's Westernization policy.
On his return he submitted a memorial to the cabinet opposing a treaty revision plan that would appoint foreign judges, and also calling for freedom of speech. Criticizing the cabinet while a minister brought him into fierce conflict with Itō Hirobumi and Inoue Kaoru, and seeing his views rejected, he resigned. Inoue soon resigned too, and the revision plan was blocked.
He became a member of the House of Peers and, keeping his distance from both parties and the government, held firmly to judging policies by whether they served the people's interest. Respected as a senior figure from Tosa, he pursued his own political course, for example opposing tax increases. He believed that farmers who worked their own land should be protected.
He remained politically active into old age, investigating the site of the Ashio pollution incident and working hard to aid its victims. His unbending stance, such as opposing the Anglo-Japanese Alliance, sometimes drove comrades away. He died that year, and his grave was placed with those of his wife, father and adopted son on a hill near his hometown of Kubokawa.
Yoshida TōyōSaigō TakamoriSakamoto RyōmaGoto ShojiroItō HirobumiKodama GentarōInoue KaoruItagaki Taisuke
Enomoto TakeakiGodai TomoatsuInoue KaoruItagaki TaisukeSanjō SanetomiŌkuma ShigenobuYamagata AritomoEdward S. Morse
People of the Meiji period ・ People by period
Based on facts found in textbooks and biographies. Uncertain points are marked as such.