With help from his father, Shi Ji started his career as a Gentleman (郎) serving the Wu imperial palace. Later, as he grew older, he was commissioned as a commandant under the title "Commandant Who Establishes Loyalty" (建忠都尉). After his uncle Zhu Cai (朱才) died, Shi Ji was put in charge of the troops who used to be under Zhu Cai's command. In 231, he followed
Pan Jun on a campaign against rebellious local tribes in Wuling Commandery (武陵郡; around present-day
Changde,
Hunan), and became famous for his courage and strength in battle. Shi Ji subsequently served as a supervising officer in charge of dealing with bandits and robbers, and was known for sternly upholding the law. Through his actions, Shi Ji attracted the attention of
Sun Ba, the Prince of Lu, Sun Quan's fourth son. When Sun Ba visited Shi Ji in his office and offered to start a friendship with him, Shi Ji knew his place so he remained humble (e.g. remained standing when Sun Ba sat down) and politely declined. Sometime in the 240s, a power struggle broke out between Sun Ba and his third brother
Sun He, the Crown Prince, as the former wanted to seize the position of heir apparent from the latter. Two opposing factions also emerged from among Sun Quan's subjects: On one side, Shi Ji, along with
Lu Xun,
Zhuge Ke,
Gu Tan,
Zhu Ju,
Teng Yin, Ding Mi (丁密) and
Wu Can, believed that Sun He was the rightful heir apparent so they supported him. On the other side,
Bu Zhi,
Lü Dai,
Quan Cong,
Lü Ju, Sun Hong (孫弘), Quan Ji (全寄), Yang Zhu (楊笁), Wu An (吳安) and Sun Qi (孫奇) supported Sun Ba. The power struggle ended in 250 when Sun Quan deposed Sun He and replaced him with
Sun Liang, and forced Sun Ba to commit suicide. When his father Zhu Ran died in 249, Shi Ji inherited his father's peerage as the Marquis of Dangyang (當陽侯) and was subsequently promoted to General Who Pacifies
Wei (平魏將軍) and appointed as the Area Commander of Le District (樂鄉; east of present-day
Songzi,
Hubei). In 250,
Wang Chang, a senior general from Wu's rival state
Wei, led the Wei forces to attack the Wu-controlled Jiangling County (江陵縣; in present-day
Jingzhou,
Hubei). When Wang Chang was withdrawing his troops after failing to breach Jiangling County's walls, Shi Ji wrote to the Wu general
Zhuge Rong: "(Wang) Chang has come a long way; he and his men are weary and their horses have no more fodder. Heaven is on our side. I don't have enough men to attack them so I hope you can lead your troops to support me. I will attack them from the front while you can mop them up from the rear. The glory won't be only mine; this is an opportunity for us to work together." After Zhuge Rong promised to help him, Shi Ji then led his troops to attack Wang Chang and his men at Jinan (紀南), which was located about 30
li away from Jiangling County. Although Shi Ji initially had the upper hand, he ultimately lost the battle when Zhuge Rong broke his promise and did not show up to help him. After the battle, the Wu emperor
Sun Quan praised Shi Ji, but severely reprimanded Zhuge Rong and wanted to relieve him of his appointment. However, he eventually pardoned Zhuge Rong as he had to "
give face" to Zhuge Rong's brother
Zhuge Ke, whom he favoured and heavily relied on. As Shi Ji was initially already not on good terms with Zhuge Ke and Zhuge Rong, this incident further deepened the rift between him and the Zhuge brothers. ==Service under Sun Liang==