Sancho I was King of Portugal for nearly 30 years in the early Middle Ages.

He was born on Nov. 11, 1154, in Coimbra. His father was the reigning monarch, Afonso I, and his mother was Matilda of Savoy.

When Sancho was 15, he received a knighthood and became his father's second-in-command. He helped his father keep control of the newly independent Portugal, including by marrying Dulce, the younger sister of King Alfonso II of Aragon in order to secure that monarch's support.

Sancho's father died on Dec. 6, 1185, not long after holding off an intense siege from Almohad forces, and Sancho took the throne. The new king focused on ending conflict with northern neighbors Galicia and León and shoring up his southern holdings, taking back the city of Silves from Moorish forces in 1188 and ordering built new fortifications, including a castle. Those defenses lasted just three years, as the Moors took advantage of Sancho's withdrawal north repeal yet another threat from Castile and León and retook Silves, in 1191.

Despite that loss, Sancho kept the realm mostly intact and well looked after; the king also bolstered the size of the population in the north, earning him the moniker Sancho the Populator. One well-known town he set up was Guarda, in 1199.

Sancho and Dulce had 11 children, nine of whom survived into adulthood: Theresa (1175), Sancha (1180), Constanza (1182), Afonso (1185), Peter (1187), Ferdinand (1188), Mafalda (1195), Branca (1198), and Berengaria (1198).

The king took a strong liking to education and literature. He sponsored trips for a number of youths to study overseas. He also wrote poetry; his poem A Ribeirinha is thought to be the oldest known example of Portuguese poetry.

King Sancho I died on March 26, 1211. His oldest son became King Afonso II.