李林甫
Li Linfu thus made accusations to Emperor Xuanzong that Zhang and Pei were engaging in factionalism. Around the new year 737, Emperor Xuanzong removed Pei and Zhang from their chancellor posts, making them "Chengxiang" () -- the heads of the executive bureau (尚書省, "Shangshu Sheng") instead. Niu was made chancellor to replace them, serving with Li Linfu. This was often viewed by traditional historians as the turning point of Emperor Xuanzong's reign, which up to that point was considered a golden age in Chinese history, toward a path of degeneration. The Song Dynasty historian Sima Guang, in his "Zizhi Tongjian", for example, commented: