 Complete the following phrase:  Suwa Tadamasa was the eldest son of Suwa Tadamichi and became daimyō in 1840 on the retirement of his father. He was strongly supported by his uncle, Matsudaira Sadanobu and rose to the post of wakadoshiyori in 1860, jisha-bugyō in 1862 and rōjū in 1864. As this was during the tumultuous Bakumatsu period, during which time the Tokugawa shogunate was forced to sign treaties with the Western powers to end Japans self-imposed national isolation policy, Yorimasa played a role in the negotiations. Together with fellow rōjū, Makino Tadayuki of Nagaoka Domain, he strenuously opposed the 