Emperor Wu of Northern Zhou
In winter 577, Emperor Wu of Northern Zhou launched a major attack on Northern Qi's important city Pingyang (平陽, in modern Linfen, Shanxi), but despite the urgency of the matter, Gao Anagong delayed notification to Gao Wei, who was then hunting with his favorite concubine Consort Feng Xiaolian at Qilian Lake (祁連池, in modern Xinzhou). He did not inform Gao Wei of the attack until Pingyang fell. During the subsequent struggle for Pingyang, Gao Anagong began secret communications with Northern Zhou forces, and the communications intensified after Gao Wei abandoned the secondary capital Jinyang (晉陽, in modern Taiyuan, Shanxi) around the new year 578, fleeing back to Yecheng.