Fang Xuanling
The Tang dynasty historian Fang Xuanling, who was the lead editor of Sima Yi's biography in the "Book of Jin", noted that Sima Yi was known for appearing to be generous and magnanimous on the outside while being distrustful and jealous on the inside. He wrote that Sima Yi was suspicious, calculative, manipulative, and a skilled practitioner of power politics. He also pointed out Sima Yi's cruelty in massacring Liaodong's population and exterminating Cao Shuang and his entire clan.