Gibraltar, a dramatic rocky peninsula protruding into the Mediterranean Sea, became famous in the 18th century as an "impregnable" fortress after it resisted several sieges. The fortress owed its strength mainly to its geographical position. The peninsula can only be accessed along a narrow isthmus from the mainland to the north. This isthmus is overlooked by the rock. The rock itself is shear on the east side and the north, so it was virtually impossible to attack from those directions. A narrow strip of flat land on the west side is the only way onto the peninsula from the isthmus, and this area is occupied by the town.
The first fortifications were built by the Moors in the Middle Ages. The Moorish town stretched across the narrow flat area of land from the sea to the lower slopes of the rock, blocking the route from the isthmus onto the peninsula. The highest point was the castle, which in turn was dominated by a large square keep known as the Tower of Homage. The northern walls, known as the land front, were the most important part of the fortifications and they remained so throughout the history of the fortress. In medieval times Gibraltar saw various sieges and changed hands several times before finally becoming part of Kingdom of Spain at the start of the 16th century.
Artillery fortifications were slow to appear in Gibraltar. The first works were built in the mid-16th century following a raid by Moorish pirates. These were carried out by the Italian engineer Giovanni Battista Calvi and consisted of a wall protecting the south end of the town. This wall, known as the Charles V Wall, extended all the way to the top of the Rock. It was stepped, with guns mounted in the flanks. The wall blocked any attack by troops landed on the south end of the peninsula, which is what the Moors had done in 1540. In the late 16th century another wall (the Philip II Wall was built behind the Charles V Wall on the upper slopes of the Rock, as a second line of defence.
The next artillery adaptations were designed by another Italian engineer, Giacomo Fratino, who transformed a tower at the north-east corner of the town into a bastion, the Baluarte San Pablo and built a small bastion at the south-west corner, the Baluarte de Nuestra Señora del Rosario. These bastions were important because they flanked the vulnerable north and south ends of the town, as well as the west side, which faced the sea.
It seems likely that Daniel Specklin, the German fortification theorist, was also involved in improving the fortifications of Gibraltar in the 16th century, although this is unproven. It is thought that his contributions were enlarging the Baluarte de Nuestra Señora del Rosario and constructing a new bastion on the south wall, the Baluarte Santiago. Finally in the 1620s the walls on the west side of the town, facing over the bay, were improved by the constuction of artillery platforms.
In 1704, during the War of the Spanish Succession, an Anglo-Dutch force landed and captured Gibraltar. The town surrendered quickly due to the poor state of the fortifications and the low morale of the defenders. The same year a Spanish force counter-attacked and the Anglo-Dutch garrison held out. In 1713 at the Treay of Utrecht Gibraltar was ceded permanently to Britain. Gibraltar was a valuable naval base in the Mediterranean, and the British soon set to work improving the fortifications.
Since the Royal Navy was strong in the 18th century, most of the effort went into reinforcing the north front, which protected the only land approach to the town. One of the ways that this front was strengthened was to mount guns on the old mole, a mole extending into the sea near the north bastion. This battery, known as the Devil's Tongue provided valuable extra firepower to support the land front. Secondly guns were mounted along the curtain wall of the land front itself. This became known as the Grand Battery. Another simple improvement was the excavation of an inundation just north of the land front. This area of flooded ground made it even harder for an attacker to advance along the narrow strip of land between the sea and the Rock.
To the east of the inundation there was a shear cliff, which was scarped by the British to make it impossible to climb. At the top of this cliff, where the ground slopes up to the top of the Rock, was a line of fortifications overlooking the approach to the land front. These lines had existed before the arrival of the British, but they were greatly strengthened during the 18th century. Known as the King's Lines and the Queen's Lines, they enabled infantry to pour fire down on the flank of any attack against the land front. Slightly higher and behind these lines were the Prince's Lines, which had the same function. With the aid of the improved defences the garrison was able to resist a four-month siege by the Spanish in 1727.
In the 1770s the British engineer Major Green made improvements to the seaward walls of the town, which became known as the Line Wall. His biggest contribution in this area was the large King's Bastion, which projected into the sea half way along the Line Wall and formed a platform for artillery to protect against a coastal attack. Built into its walls were casemated rooms that could hold 800 men and stores for ammunition.
In June 1779 a Spanish force laid siege to Gibraltar, marking the start of what became known as the Great Siege. Gibraltar held out until the war ended the 3 years and 7 months later, which earned it the reputation of being an impregnable fortress. The Great Siege saw the fortifications of Gibraltar tested by attacks from the isthmus and from the sea. Two important changes were made during the siege that were born of a necessity to improve the coverage of the batteries on the north face of the Rock.
Firstly, in February 1782 a new type of gun carriage was introduced in the batteries on the Rock. The gunners in these batteries had the problem that their targets were a long way below them, and standard guns could not be depressed sufficiently to cover the ground closer to the Rock itself. To solve this problem Lt Koehler invented a special carriage to enable guns to be fired at steep angles from the high batteries.
Secondly, a tunnel was dug in the north face of the Rock. This was done in response to a specific problem. The Spanish were able to exploit the ground at the foot of the north-east face of the Rock, which was out of view of any of the guns in the land front defences or the batteries on the Rock itself. To counter this, the governor offered a reward for anyone who could find a way of mounting a gun on an outcrop known as The Notch. Sgt Maj Ince proposed digging a tunnel through the rock in order to do this. The original intention was simply to tunnel through the rock to The Notch and then mount guns on top of it. However, the tunnelers found that the build up of dust required a ventilation opening in the north cliff face. When this opening was made, it was decided to mount a gun to fire through the opening. In the end, a whole series of guns were mounted along the tunnel.
The war ended in February 1783, bringing an end to the siege before the tunnel had reached The Notch, but work continued in peacetime. As work continued the engineers decided not to mount guns on top of The Notch but to tunnel inside it instead. The resulting gallery, St George's Hall, was completed in the 1780s. It mounted 7 guns and covered the ground on the north side of the Rock. It was followed by more tunnels and guns in the north cliff face. The tunnel systems were interlinked and had their own powder magazines. An attacker on the isthmus had no way of neutralising these guns, since they fired through small openings in the cliff face itself.
Various reinforcements were made to Gibraltar's fortifications at the end of the 18th century and the beginning of the 19th century. This was the time of the Napoleonic Wars, when British and Spanish forces fought against the French in Spain. Although Gibraltar was not attacked, it was an important British garrison throughout the wars. This period saw counterguards and tenailles constructed in front of the bastions on the Line Wall, giving the fortifications an extra layer of defences facing the sea.
The next wave of reinforcements came in the 1840s. Gen Sir John Jones made several recommendations for improving the fortifications in the face of steam ships and more powerful artillery. Much of the Line Wall was remodelled, the trace being modified in places and casemates built into the bastion flanks. This included a front of two demi-bastions, the Wellington Front, which replaced what was previously a rather long curtain.
Another recommendation of Gen Sir John Jones was the construction of retired batteries. These batteries were built further up the slope of the Rock, away from the shoreline. This took advantage of the more powerful artillery and made the batteries themselves more difficult to see from the water. A number of retired batteries were built on the slopes of the Rock facing east over the harbour.
The 19th century saw more changes as the Line Wall defences were modified to take more powerful guns. Coastal batteries were built all over the Rock to cover the Straits of Gibraltar and protect against a coastal bombardment. The bastioned defences became obselete, but they were left in place and guns were still mounted on them in the Second World War.
The bastioned fortifications of Gibraltar are remarkably complete. The defences of the town itself suffered from urban expansion in the 20th century some of the bastions were built on. However, this trend is now being reversed and the walls are slowly being cleared and restored. The old generating station that was built on King's Bastion has been removed recently and the bastion is now home to a leisure centre and some bars, which have been integrated into the restored structure.
The land to the west of the old town has been reclaimed, so the sea no longer comes up to the walls. This makes it hard to imagine their role as coastal defences and leaves the remains of the Devil's Tongue Battery strangely isolated next to a road. The Moorish Castle is also largely intact, but is crowded by modern buildings on the lower slopes. Part of it is home to a prison, but the upper part and the Tower of Homage can be visited. The King's, Queen's and Prince's Lines are still intact, but they are very overgrown. Hopefully one day they too will be restored and opened to the public.
The tunnels made during the Great Siege is open to visitors and is a short (but steep) walk from the castle. They are an impressive feat of engineering and it is easy to understand how important they were for the defence of the fortress against an attack from the isthmus. To the south, the Charles V wall is in good condition. It is possible to walk all the way from the town to the top of the Rock up the wall, which has had a handrail added recently. This is a long climb and not recommended in the hot weather. One of the best ways to visit the Rock is to take the cable car from the town up to the top. It is then possible to walk down the Charles V wall back into the town, or along the Rock to the Moorish Castle and Great Siege Tunnels. A ticket for the Upper Rock costs about £10 and includes entry to the main attractions on the Rock, such as the Moorish Castle, the tunnels and the military museum. Not included is the Gibraltar Museum, in the town. This museum has various exhibits from Gibraltar's history, including a large model of the Rock and its fortifications that was made in 1865. A valuable piece of advice is to buy one of the maps that are dispensed by small machines in the town. The ones given out by the tourist information are hopelessly inaccurate in their depiction of the roads on the upper Rock.
Gibraltar is a British Overseas Territory and there is a border control, so visitors crossing from Spain will require passports. Making a day trip into Gibraltar with a car in the summer can be difficult due to the large queues that can form at the border. It is possible to avoid these by taking a bus or simply parking in Spain and walking into Gibraltar.
A visit to Gibraltar, one of the most impressive fortified places in Europe, is well worth the trip for any fortress enthusiast. There are well preserved fortifications dating from medieval times to early 20th century batteries. This article has focussed on the defences of the town itself, but the south end of the peninsula has fortifications of its own which are also worth exploring.
Discover Gibraltar - a very good website with information on the fortifications and on visiting Gibraltar.