Although their empire had been defeated by the Muslim onslaught, individual Visigothic nobles resisted, taking refuge in the mountain stronghold of Astúrias. As early as 737, the Visigothic noble Pelayo took the offensive and defeated the Muslims at Covadonga, for which he was proclaimed king of Astúrias, later León. Subsequent kings of Astúrias-León, who claimed succession from Visigothic monarchs, were able to retake Braga, Porto, Viseu, and Guimarães in northern Portugal, where they settled Christians around strongholds. For 200 years, this region was a buffer zone across which the frontier between Christians and Muslims shifted back and forth with the ebb and flow of attack and counterattack.

The creation of Portugal as an independent monarchy is clearly associated with the organization of the military frontier against the Muslims in this area. This buffer zone between Christian and Muslim territory was constantly being reorganized under counts appointed by the kings of León. The territory known as Portucalense was made a province of León and placed under the control of counts, who governed with a substantial degree of autonomy because of the province's separation from León by rugged mountains.

In 1096 Alfonso VI, king of León, gave hereditary title to the province of Portucalense and Coimbra as dowry to the crusader-knight Henry, brother of the duke of Burgundy, upon his marriage to the king's illegitimate but favorite daughter, Teresa. Although Henry was to be sovereign in Portucalense, it was recognized by all parties that he held this province as a vassal of the Leonese king. Henry set up his court at Guimarães near Braga. He surrounded himself with local barons, appointed them to the chief provincial offices, and rewarded them with lands. Bound by the usual ties of vassal to suzerain, Henry was expected to be loyal to Alfonso and render him service whenever required. Until Alfonso's death in 1109, Henry dutifully carried out his feudal obligations by attending royal councils and providing military assistance in the king's campaigns against the Muslims. Alfonso's death plunged the kingdom of León into a civil war among Aragonese, Galician, and Castilian barons who desired the crown. Count Henry carefully stayed neutral during this struggle and gradually stopped fulfilling his feudal obligations. When he died in 1112, his wife, Teresa, inherited the county and initially followed her husband's policy of nonalignment.

The victor in the struggle for the Leonese crown was Alfonso VII, who, when he ascended the throne, decided to assert his suzerainity over Teresa, his aunt, and her consort, a Galician nobleman named Fernando Peres. Teresa refused to do homage and was forced into submission after a six-week war in 1127. Her barons, who saw their fortunes and independence declining, took this opportunity to align themselves with her son and the heir to the province, Afonso Henriques, who had armed himself as a knight. Supported by the barons and lower nobility, Afonso Henriques rebelled against his mother's rule. On July 24, 1128, he defeated Teresa's army at São Mamede near Guimarães and expelled her to Galicia, where she died in exile. Afonso Henriques thus gained control of the province of Portucalense, or Portugal, as it was known in the vernacular.

Data as of January 1993