Some scholars believe that the Soga were an immigrant family from the Korean peninsula. They moved to the Soga region of the Yamato state in central Japan and formed alliances with immigrants from the Korean kingdoms, providing scribal and managerial technical skills.
The Soga clan’s rise to power began with Soga no Iname, the head of the clan and the first Soga to hold the position of grand minister. He was victorious in the policy debates of 540 c.e. and married two of his daughters to Emperor Kimmei. However, neither of Iname’s grandsons became heir to the throne.
The next Soga clan head, Soga no Umako, also grand minister, succeeded in marrying one of his daughters to Kimmei’s son, King Bidatsu, and the couple produced a son who was one of three candidates for the throne.
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The Soga candidate was eventually enthroned as emperor Yômei after fierce military battles between the Soga clan and their rivals, the Mononobe, who also supplied a male heir to the throne through a Mononobe woman. Yômei took another daughter of Soga no Iname to be his queen, and the two produced the famous prince Shôtoku Taishi.
The victory was short lived however when Yômei fell ill, and fighting between the Soga and Mononobe resurfaced. Again the Soga were victorious, and another male offspring of a Soga woman became the sovereign King Sushun. Once the main line of the Mononobe was massacred in 587 the Soga dominated court affairs.
Despite Sushun’s connection to the Soga, rumors spread that Sushun would betray his uncle Umako, so Umako had him assassinated and Sushun’s consort, Suiko, became empress. Suiko ruled alongside her son and regent, Shôtoku, during a time when the Soga clan heads Emishi and his son Iruka attempted to assert Soga dominance by levying taxes and trying to expand their lands.
Suiko, despite being a part of the Soga, refused requests to expand Soga lands. Iruka even killed Prince Shôtoku’s son. Histories of the time criticize the Soga for trying to become monarchs. The most tyrannical of the Soga patriarchs, Iruka, was assassinated in 645 in a palace coup that effectively ended the Soga rule.
The significance of the Soga dynasty was their importation of culture, government, and religion from China and Korea and their influence in domestic politics through marriage arrangements and intrafamilial assassination.
The Soga supported Buddhism over other forms of court-related native religions, creating several large Buddhist temples, statues, and bells that attested to their power in the physical and spiritual realms. This support for Buddhism further antagonized other clans, who often held key religious-political positions.