Chang Yu worked in the Department of Visiting Guests (객성; 客省; kaeksŏng), during the reign of King Gwangjong.
[2] In 1010, Chang Yŏn-u was serving as the deputy minister of War (병부시랑; 兵部侍郞; pyŏngbu sirang) when he was appointed as the haengyŏng tot'ongbusa (행영도통부사; 行營都統副使) of the 300 thousand strong Goryeo army led by Kang Cho sent to defend against the invading Khitans.
He was appointed as the superintendent of the Censorate (판어사대사; 判御史臺事; p'an ŏsadae sa) for his service to the king.
Chang was appointed as the Minister of Revenue (호부상서; 戶部尙書; hobu sangsŏ), but died shortly later on January 5, 1016 [nb 1].
[1] Chang's poem, "Song of Cold Pine Pavilion" (한송정곡; 寒松亭曲), would later be included in the Joseon-era collection of writings called Tongmunsŏn (Selections of Refined Literature of Korea).