Pei Ju
In his youth, Pei Ju was known for his knowledge and intelligence. He served on the staff of Gao Zhen (高貞) the Prince of Beiping and then of Gao Renying (高仁英) the Prince of Gaoping, both sons of Emperor Wucheng of Northern Qi. After Northern Qi was destroyed by rival Northern Zhou in 577, it was said that Pei was stuck at his position. When the Northern Zhou general Yang Jian served as the commandant at Ding Province (定州, roughly modern Baoding, Hebei), he invited Pei to serve as his secretary. Pei later left Yang Jian's service when his mother died, to observe a mourning period. In 580, Yang Jian seized power as regent over the young Emperor Jing of Northern Zhou. He sent messengers to summon Pei, and Pei served on his staff as a secretary.