57. Hondarribia. The Queen's Bastion with its sentry box.© Gorka Agirre

Gipuzkoa had two fortified towns with bastion fortifications: Hondarribia and San Sebastian. The former was the more important in the sixteenth and seventeenth centuries because it overlooked the French border; the latter became particularly relevant in the eighteenth century. The port of Getaria and the overlooking hill of San Anton were also the subjects of modern military engineering, but the work was minor.

58. Plan of San Sebastian drawn in 1724 by Juan de Landaeta. In this project, the fortifications on Mount Urgull are arranged in three concentric areas overlooked by Holy Cross Castle.© Carlos Mengs

Experience had shown that if artillery shells were to be stopped, the original walls would have to be more than doubled and military engineers began to design walls over 15 metres in thickness.

There were significant technical and financial drawbacks to building such constructions in stone, and the usual arrangement consisted of a thick outer wall of ordinary masonry (sometimes reinforced with buttresses) dressed on the outside with ashlar stonework. Behind the stone wall there was a large mass of earth (terreplein) ending in a slope or, if there was not enough room, a containing wall.

59. Western section of the fortifications of San Sebastian. The piles used in areas exposed to incursions from the sea can be seen:
B) Imperial Turret;
C) St. Philip's Bastion;
E) Counterguard with sentry box;
M) St. Charles' Hornwork;
N) Ravelin;
F) Tierra [Land] Gate;
G) Sea wall.© Hergara S.A.

On top of this thick wall a parapet, some 5 or 6 metres thick and 2 metres high was erected, leaving enough room (adarve) to install the guns and for troops to move about. Outside, the wall and the beginning of the parapet were completed with a semicircular moulding known as a cordon or stringcourse.

60. Drawing of the sentry box on the Governor's Bastion in San Sebastian (1735).© Hergara S.A.

The parapet had trapezoidal gun emplacements, to allow the guns, positioned on platforms, to be fired in different directions. A banquette adjoining the parapet was another frequent feature.

The towers of the mediaeval wall were replaced in these new fortifications by turrets (or cubos) - large round towers no higher than the wall. In general, they were designed to house several guns. Examples of this feature are the Amezketa and Los Hornos turrets in San Sebastian, the cubo of Bamba in Hondarribia and the turrets on the Gazteluzar castle in Irun. The drawback of these turrets was that they created areas which could not be defended, and they were soon replaced by bastions. Modern fortifications are consequently known as bastioned fortifications.

A typical bastion is pentagonal in shape, and lower than the wall into which it is set; this allows defenders to fire over it and offers less of a target to enemy gunners. Each of the walls of the bastion facing the area outside the fortified area is known as a face while the walls perpendicular to the main wall are called flanks. The latter could be used to prevent an enemy from approaching the wall, either by firing from the adarve, or from casemates in the flanks with gun emplacements. On occasions the faces were extended slightly towards the wall, to form an orillion which protected the flank from the impact of enemy artillery. The fifth side, imbricated in the wall, is known as a gorge. If the bastions were properly positioned, they could defend each other, thus preventing the dead angles created between towers and turrets.

62. 'Plaça de Fuenterrabía' / Leonardus Ferraris faciebat. - 1640.© Martín Izagirre

When the terrepleins of the bastions were very thick they completely filled the inside. Otherwise, they formed an empty central space, occupied by doors, gardens, barracks, powder stores, etc.

Bastion fortifications were surrounded by a fosse and by the outer fortifications. The purpose of these constructions was to delay any assault on the main part of the stronghold, so that if the enemy was on the point of taking an outer section, the defenders occupying it could move back to another of the outer fortifications or ultimately to the main area of the stronghold, thus allowing the final assault to be put off and helping to exhaust the besieging troops.

The outer fortifications had to fulfil on main rule: in the event that enemy troops succeeded in taking them, it must be entirely impossible for them to use the outer fortifications to attack the inner ones - or the main wall itself. For this reason, outer ramparts never had parapets facing inwards towards the stronghold, and the enemy were therefore at the mercy of defensive fire from the fortifications further back. The outer fortifications were linked to the rest of the structure by stairs, ramps, double caponiers, bridges, posterns, etc., to allow rapid advance or retreat.

61. Plan of the town of San Sebastian (1775) by Carlos Agustín Giraud.© Carlos Mengs

The most common features of the outer fortifications are: counterguards, hornworks, ravelins, covered ways and glacis.

The countergaurds were formed of two curtains facing away from the faces of the bastion. The hornworks consisted of two demi-bastions (also called half bastions) joined by a curtain from which curtain walls (wings) ran towards the main fortification, without actually extending as far as it. The ravelins were designed to protect the curtains and were formed by two faces (and normally by two flanks). The demilunes played a similar role. They had no flanks but had a curving terreplein running towards the stronghold.

The covered ways consisted of a narrow slope running along the outermost part of the outer fortifications. On their inside there was a fosse, and on the outside a fusiliers' parapet surmounting the glacis. Generally they are interrupted (at least partially) by traverses (earthen mounds to prevent enfilade fire from the enemy) and small parade squares.

The glacis is a gentle slope running down from the parapet of the covered way towards the exterior. It was of vital importance that it should be kept free of obstacles, so that the enemy would be unprotected at all times and the defenders could rebuff any approach by firing on it.

Fortified towns often contained a strongly fortified enclosure used exclusively for military use, known as a citadel. This was intended to serve as the last stronghold of defending troops or to control the civil population at times of popular uprising. Citadels are commonly pentagonal in shape (as is the case of the magnificent example in Pamplona). Others, however, are irregular in shape, as is the case in San Sebastian, where the fortifications on Mount Urgull acted as an unofficial citadel.