Sima Yi
When Sima Yi started planning a coup d'état against Cao Shuang; according to the "Jin Shu", Sima Yi confided only in Sima Shi, excluding even Shi's younger brother Sima Zhao from the discussion (although Sima Guang found this unlikely and, in his "Zizhi Tongjian", opined that Sima Yi planned the coup with both Sima Shi and Sima Zhao). Sima Shi put together a group of 3,000 loyal men without knowledge by Cao Shuang or his associates, and when Sima Yi set to carry out his plans in 249, Sima Shi was able to quickly summon the men to carry out the coup.