Castilian Reconquista Frontier

Timeline

1. 1085–1150Toledo · CastileAfter Alfonso VI recovered Toledo, the Castilian frontier shifted far south; Christian settler colonization and castle building advanced to the south bank of the Tagus, forming a new military boundary between the Muslim Almoravids and the Christian kingdoms.
2. c. 1171–1177Sierra Morena · SpainAfter the Almohad dynasty invaded Iberia from North Africa and counterattacked Christian lands, Castilian frontier castles faced sustained pressure; Alfonso VIII organized defenses in the 1170s and sought alliances with León, Aragon and the papacy against the Muslim unified offensive.
3. c. 1175–1180Southern Castilian frontier · CastileCastile built chains of castles on the frontier and granted defensive territories to military orders such as Calatrava and Santiago; frontier nobles bore seasonal campaign obligations, forming an expansion frontier mechanism combining Christian settlement and military garrison.
4. 1212–1250Las Navas de Tolosa · SpainAlfonso VIII and a Christian coalition defeated the Almohad army at the Battle of Las Navas, shifting the Castilian Reconquista frontier far south to the Guadalquivir line, paving the way for the fall of Córdoba and Seville in the 13th century.