Jeongjong, 10th monarch of Goryeo
Jeongjong of Goryeo (31 August 1018 – 24 June 1046) (r. 1034–1046) was the 10th ruler of the Goryeo dynasty of Korea. He was the second son of Hyeonjong, and the younger brother of Deokjong. At the age of four in 1022, he was made "Naesaryeong", a position of high rank, and designated the Prince of Pyongyang. Jeongjong was greatly concerned with national defense, and began constructing fortresses along the northern border in the first year of his reign. In 1037, the country suffered an invasion from the northern Khitan tribes. In 1044, the Cheolli Jangseong  was completed, an enormous wall across northern Korea. Jeongjong also concerned himself with the material support of the army, distributing state land to indigent soldiers in 1036. Just before his death in 1046, Jeongjong established primogeniture as national law.