The Spanish Lines spanned the isthmus at a distance of between eighteen hundred and two thousand yards from the northern defences of Gibraltar. The map above has been rendered from an original map showing the various fortifications in 1782.
On the eastern seaboard stood Fort Santa Barbara, a well built permanent pentagonal structure with a bastion, a dry ditch, a covered way and a glacis. The photograph below shows the model of the fort which is on view at the La Linea Museum. The model is about 80 percent correct in its detail.
The fort had embrasures for twenty-four guns and its two eastern faces looking out over the Mediterranean where its guns could menace British ships and part of the eastern side of the Rock. The range was about halfway along the length of the peninsula.
At the beginning of the 19th century, due to the invasion of the Napoleonic troops, Spain signed an alliance of mutual defence with England. The English profited from this and were allowed to destroy the fortifications of La Linea to prevent them being used by the French. The photographs above and below show the extent of this destruction.
The supports for the original entrance bridge are still in good condition, these can be seen in the photograph below. The view of the Rock is clearly seen in the photograph.
In the months preceding the Second World War, Spain gave priority to the design of a defensive system to protect all its frontiers, and in La Linea a number of new fortifications were built almost on top of the earlier ruins. Below you can see the rear view of a line of six gun positions. These are explained more fully in the section on WW2 Bunkers (B) above.
Fort San Felipe stood at the western end of the Line, this was a broader design with two faces containing twenty-eight gun positions. It too had a ditch and a bastion. The breadth of its front allowed it a wide arc of fire across the Bay of Gibraltar, and its guns could bombard the town and rake the British battery on the Old Mole. The photograph below shows what little remains of this today. These will soon be covered by new buildings in the near future.
In the months preceding the Second World War, Spain gave priority to the design of a defensive system to protect all its frontiers. In order to study the technical details of the project, a Commission of military experts, directed under the ruling of General Pedro Jevenois, was designated. Following its conclusions, they planned and drew up fortification works which were developed between 1940 and 1944.
Basically, the defensive system of the so called "South Frontier" included the Gibraltar frontier, and a flank protection which ran along the immediate coast, east and west of this position. The tactical concept was that of the "defence in depth" through which the different elements were not set out to contain the enemy in a fixed line, but to absorb the drive of its assault and to allow a subsequent overturning through a counterattack. It is a typical concept of the German school and the Spanish army adopted it in the 1930s.
Units of Spanish sappers and battalions of civil workers under military rulings spent various years working on the project which would end up covering the coastline with artillery positions, machine gun nests, watchtowers, switchboards, command posts etc. Nearly 500 bunkers of various types were constructed.
The central position, at the isthmus, contained 27 different bunkers associated with three very well defined zones, the first zone was made up of two mined barriers as well as "Dragon Teeth" and "Obstacle Lanes" composed of thick metal stakes reinforced with barbed wire. There are no surviving remains of these.
The second zone contained the domed machine gun positions which still exist today. The object rotation opposite shows the model in the La Linea Museum. Their mission was to contain the assault of an infantry force and provide close protection to the artillery positions nearby. Four of these machine gun nests still survive, they are all in Reina Sofia Park opposite Gibraltar. Three of them are complete and the forth has lost a dome due to redevelopment in the 1980s.
The third zone consisted of a shielded concrete artillery line. Its total equipment consisted of 35 pieces, 27 of which were 66mm infantry cannons. Three of the five big artillery blocks still survive in the area of Fort Santa Barbara. The photographs below show the existing remains close to the old fort. These constructions where built on the ancient walls of the 18th century line. A two-floor command post also survives in a street called Banqueta Avenue in the area behind the Museum.
In the summer of 1940 after the defeat of France by Germany, General Franco impressed by the recent triumphs of the Wehrmacht, decided to realise his territorial ambitions by forming an alliance with Hitler. But at that time, Germany had other priorities and did not have an interest in the control of the Mediterranean until all attempts to get a British surrender had failed. The German State opted for what they called the Peripheral Strategy which hit routes which joined Great Britain with its Empire. It was then, in the Autumn-Winter of 1940 when the Rock became the major objective, and the isthmus fortifications became important.
As a consequence, besides spies and British, Italian or German observers, the bunkers in construction were examined by officials from the Wehrmacht who were sent by German High Command to study the aspects of a future operation to take Gibraltar. This operation was called Operation Felix, it required the entrance of Spain into the war but he possibilities of the start of this offensive were delayed as a result of a meeting between General Franco and Hitler, it has been said that Franco was worried about having German troops on Spanish soil.
With the opening of the Russian front in June 1941, the fortifications in La Linea ceased to be a threat in the short term. And as the Russian front became a failure for Germany the isthmus Bunkers were seen as just a defensive measure facing the possibility that the allied assault on Europe would come together with an action against Spain.
In November 1942, with the major support of Gibraltar and its new airfield, the allied forces launched Operation Torch in North Africa. At this time, one of the greatest fears of General Eisenhower, Commander in Chief of the Allied Forces during this operation, revolved around the possibility that the Spanish could hamper the operation from their fortified positions on the isthmus.
The defeat of Italy in 1943 distanced the Straits from a war that would end two years later. The Bunkers surrounding the isthmus became, over time, a distant legacy of the war.