O-Ie Sōdō
was the 6th "daimyō" of Suwa and hereditary chieftain of the Suwa clan. Tadaatsu was the fourth son of Suwa Tadatoki, and became "daimyō" on Tadatoki's retirement in 1763. He attempted to reform the domain's finances, but only succeeded in splitting his senior retainers into pro-reform and anti-reform factions. This resulted in an "O-Ie Sōdō" which further paralyzed the domain administration. Tadakatsu was forced into retirement in 1781, and several members of the pro-reform faction were forced to commit "seppuku" the following year. Tadaatsu died in 1812 at the age of 67. He was married to a daughter of Abe Masayoshi of Fukuyama Domain.