During the First Carlist War (1832-1839) a large number of field (or provisional) fortifications were built on the many hills overlooking the main towns and roads in Gipuzkoa. Depending on their features, they were called forts, batteries, redoubts or blockhouses. In addition, many trenches and other minor fortifications were also built.
A fosse was generally dug around these fortifications and the earth was used to form a polygonal parapet containing between two and five gun emplacements with their corresponding platforms for the guns (between one and three).
In the middle of the fortification there were normally two buildings. The larger of these acted as a barracks for the garrison and often made use of some existing building. Another, much smaller, building was used to store ammunition. A wooden bridge, which could usually be raised, afforded access to the fortification across the fosse.
Various urban nuclei were fortified and in some field forts and other fortifications were built. This was the case, for example, of Hernani (with the Daoiz, Tolosa, St. Barbara, Yarzagaña, Los Arcos, Iribarren, Aramburu, Oriamendi and O'Donell forts) and Irun (Parque, Conrad, Mendibil and Evans forts) and on the Carlist side, Andoain (with the Holy Cross redoubt and the King's, Dolores and Zumalakarregi forts).
San Sebastian still had its defensive bastions when the war began in 1833. Consequently, no large-scale investments were needed to fortify the city centre itself. However in the environs of the town and in the port of Pasaia [Pasajes], about twenty fortifications had to be built. These included the Farola, Windmill, Puio, Katxola, Ametzagaña, Cristina, Queen's, St. Martin's, Alza and Lord John Hay forts; the Aranjuez, Torres, Bordandia and English batteries and the Ametza, Rodil, St. Francis, Elizabeth, St. Anthony and Morales redoubts.
After the end of the war the fortifications were destroyed by Royal Order, and for this reason practically no remains can now be seen.