Following the Meiji Restoration, Soejima became a government official, helping to draft the Seitaisho ("Document on Form of Government"), one of the central governing documents of the new government, in 1868 alongside Fukuoka Takachika. He rose quickly to become Foreign Minister in 1871, the same year that a number of Miyako Islanders were killed by Taiwanese aborigines, in an incident which would quickly develop into serious tensions with the Chinese government.
The following year, in 1872, a Peruvian ship called the Maria Luz made harbor at Yokohama, sparking a diplomatic incident when Chinese coolies on board claimed they were being mistreated and requested aid from the Japanese government.
In 1873, Soejima joined Japanese Diplomatic Minister in China Yanagihara Sakimitsu in meeting with Chinese officials in Beijing to discuss the 1871 Taiwan incident. The Chinese asserted that they did not exercise effective control over those regions of Taiwan and thus could not be held responsible for the actions of the aborigines (and thus could not be expected to pay reparations). Soejima had already been advised by Charles DeLong, US Diplomatic Minister resident in Japan, that under Western ("modern") systems of international law, this constituted a disavowal of sovereignty, meaning that the relevant portions of Taiwan were now legally up for grabs. Amidst this situation, Soejima suggested that if China claimed no responsibility for the aborigines, then surely they wouldn't mind the Japanese dispatching a punitive mission; the Chinese countered, however, that the Ryukyuans killed were Qing vassals and not Japanese Imperial subjects. Ultimately, in accordance with Soejima's hawkish desires, a punitive missions would be launched, in 1874.
However, in the meantime, Soejima stood alongside Saigô Takamori, Etô Shinpei and others in 1873 in advocating for an invasion of Korea, and for deploying troops to defend Sakhalin against Russian advances. After the majority of oligarchs ultimately rejected both of these ideas, Soejima joined Saigô, Etô, and others in resigning from government. The following year he helped establish a political party called the Public Patriots' Party (Aikoku kôtô), and along with Itagaki Taisuke and Gotô Shôjirô, submitted a Petition for the Establishment of a Popularly Elected Assembly to the Meiji government.
Soejima later returned to public service, serving as a councilor within the Imperial Court, and as a member and then Vice Chairman of the Privy Council, as well as in the position of Home Minister under Prime Minister Matsukata Masayoshi.
Soejima died on January 31, 1905.
- "Soejima Taneomi," Kindai Nihonjin no shôzô, National Diet Library, 2013.
- Takashi Fujitani, Splendid Monarchy, UC Press (1998), 63-65.