Theresa was Countess of Portugal, and for a time claimant to be its independent Queen. She rebelled against her half-sister Queen Urraca of León. She was recognised as Queen by Pope Paschal II in 1116, but was captured and forced to accept Portugal's vassalage to León in 1121, being allowed to keep her royal title. Her political alliance and amorous liaison with Galician nobleman Fernando Pérez de Traba led to her being ousted by her son, Afonso Henriques, who with the support of the Portuguese nobility and clergy, defeated her at the Battle of São Mamede in 1128.

Portugal, officially the Portuguese Republic, is a country located on the Iberian Peninsula, in Southwestern Europe, and whose territory also includes the Macaronesian archipelagos of the Azores and Madeira. It features the westernmost point in continental Europe, its mainland west and south border with the North Atlantic Ocean and in the north and east, the Portugal-Spain border constitutes the longest uninterrupted border-line in the European Union. Its archipelagos form two autonomous regions with their own regional governments. In the mainland, Alentejo region occupies the biggest area but is one of the regions in Europe with a lower population density. Lisbon is the capital and largest city by population, being also the main spot for tourists alongside Porto and Algarve.