Portugal emerged as a country in 1143, subsequent to a 15-year revolt by Dom Afonso Henriques. Afonso Henriques overpowered his mother Countess Teresa of Portugal, regent of the County of Portugal and loyal to the Kingdom of Leon at the battle of Sao Mamede close to the town of Guimaraes, in June of 1128. Countess Teresa was jailed and exiled by her son. She died in 1130. Hence, Guimaraes is known as the birthplace city of Portugal. Yet, the true test of a sovereign nation did not take place until 1385. In 1385, Joao Mestre de Avis with the aid of legendary supreme constable, Nuno Alvares Pereira overpowered the Castilians at the epic Aljubarrota battle, where the Castilians outnumbered the Portuguese 6:1.