Yang Guozhong
As of 754, the chancellor in power was Yang Guozhong (Li Linfu having died in 752), the cousin of Emperor Xuanzong's then-favorite concubine Yang Guifei (unrelated to Li Heng's mother). Yang Guozhong and An were locked in a power struggle, and Yang repeatedly accused An of plotting a rebellion, but Emperor Xuanzong would not believe it, although Li Heng eventually came to agree with Yang Guozhong. In late 755, with Yang Guozhong repeatedly trying to provoke An into a rebellion, An finally did, from his base at Fanyang (范陽, in modern Beijing). After the rebellion started, Emperor Xuanzong briefly considered making Li Heng regent, but at the pleas of Consort Yang and her three sisters (who were fearful that Li Heng would act against them if he had regent powers), did not actually do so.