La frontera del Alentejo durante la Guerra de Restauración (1640- 1668)

The need for the Portuguese Restoration War arose between 1640 and 1668, becoming imperative the defence of the Alentejo border through the adaptation of old military defences and the elaboration of new projects. Thus, it is noted that some military engineers, who were working on the adaptation of Alentejo fortifications at the time, began to serve the Castilian enemy, making their projects to be modified. The mobility between Portuguese and Castilian people during this period are also highlighted, indicating concrete examples. Border crossings and assaults are taking into account to control the correspondence between both kingdoms. This control also allows us to analyse the situation of the enemy, being possible to know their strategic position, if they would be close to the well-organized border places, as well as the number of men and the weapons they would have. These analyses will be made from original documentation existing in the National Archive of Torre do Tombo, in Lisbon, in the Public Library of Evora, and in the General Archive of Simancas.