房玄龄
After the submission of Xu Shiji (who later would be bestowed the imperial clan name of Li and be known as Li Shiji) to Tang, Zhang Liang was made the governor of Zheng Prefecture. However, around the same time, Wang Shichong captured Zheng Prefecture, and Zhang had nowhere to go, and instead took up guerilla warfare in the region. Later, based on recommendations by Li Shiji and Fang Xuanling, the Tang prince Li Shimin (the second son of Emperor Gaozu) invited Zhang to serve on his staff, and Zhang eventually became a trusted advisor.