Yan Song served as the chief assistant during the Jiajing period of the Ming Dynasty, but the given search results did not mention the specific time he served as the chief assistant. Therefore, I don't know exactly when Yan Song became the chief.
Xu Jie was the chief assistant behind Yan Song.
Xu Jie was the head of the cabinet after Yan Song.
Xu Jie and Li Chunfang were the two chiefs behind Yan Song. Xu Jie took over as the chief assistant of the cabinet after Yan Song abdicated, eliminating the maladministration during Yan Song's reign, and recommended Gao Gong and Zhang Juzheng to enter the cabinet. Xu Jie was diligent in government affairs and loved talents, which laid the foundation for the Wanli New Deal. Li Chunfang became the chief of the cabinet after Xu Jie, but he was mediocre and retired a few years after being suppressed by Gao Gong.
Yan Song's previous chief assistant was Xia Yan.
Yan Song had been the chief assistant for twenty years.
Xia Yan was Yan Song's previous chief assistant.
Yan Song had been the chief assistant for twenty years.
Yan Song had been the chief assistant for twenty years.
The chief assistant behind Yan Shifan was Yan Song.
Yan Shifan had once held the position of chief assistant during the Jiajing Emperor of the Ming Dynasty. Yan Shifan was the son of Yan Song, the chief assistant of the Jiajing Dynasty of the Ming Dynasty. He became an official after entering the Imperial College by borrowing his father's power. He had served as a junior official of the Shangbao Department and the left assistant minister of the Ministry of Works. When Yan Song became the chief assistant again, he handled government affairs on behalf of his father and was known as the number one genius of the Jiajing Dynasty. Therefore, it could be concluded that Yan Shifan had held the position of chief assistant in the Jiajing Dynasty.