The world’s premier natural fortress, Gibraltar has always been a tough nut to crack.

The Rock. For centuries the term meant only one place: The Rock of Gibraltar. In ancient times it formed the northern- most of the famed twin Pillars of Hercules that guarded the passage between the Mediterranean and the Atlantic (the southern pillar was a peak in Morocco). The long struggle between Moor and Christian transformed Gibraltar into a fortress, and after 1462 it became a symbol of the Spanish Reconquista. Falling under British control in 1713, Gibraltar became a point of vital strategic importance in the Age of Sail. As guardian of the route between the Mediterranean Sea and the Atlantic Ocean, Gibraltar was besieged multiple times and figured prominently in many wars.

Even after the passing of the Age of Sail, Gibraltar remained vital to the British Empire and a thorn in the side of its enemies. In both world wars it guarded Britain’s lifeline through the Suez Canal to Asia, and in the 1940s it played an important role in the life-or-death struggle against Germany’s U-boats. Since World War II, Gibraltar has become the subject of sometimes violent discord in a European Union that was formed in part to prevent territorial disputes. Spain is determined to reclaim the Rock while Great Britain, backed by the vast majority of Gibraltar’s approximately 30,000 inhabitants, stands equally determined to continue its presence there.

Literally speaking, the Rock is not Gibraltar but a part of it. Gibraltar is a roughly 2.5-square-mile peninsula protruding from the southeast coast of the much larger Iberian Peninsula. It is not quite the southernmost point of Iberia, nor does it guard the narrowest point of waterborne passage, though its tip ends just 14 miles from the coast of North Africa. But the Rock does give the peninsula its military significance. Planted squarely on the peninsula, it slopes upward 1,400 feet on its steep eastern face, making it seem custom-built to resist invasion by land. The peninsula’s settled area, such as it is, nestles safely below the Rock’s western face. Seaward to the south, the approach is not so daunting and there are tiny landing strips available to soldiers; still, a protracted campaign to capture Gibraltar from this direction would require constant support from the sea. In the Age of Sail and to a somewhat lesser extent in the 20th century, control of Gibraltar required total and prolonged naval dominance of the western Mediterranean. The maintenance of naval supremacy depended in turn on control of Gibraltar.

Until the 16th century, Gibraltar was more significant as a north-south conduit between Europe and North Africa than as a guardian on the east-west naval route. Populations moving between Iberia and North Africa passed by and may have settled in Gibraltar as a matter of course. The Romans and their successors established small posts or settlements there but did not fortify it. In the early eighth century, Muslim invaders stopped at Gibraltar briefly in the course of their conquest of Iberia. In time they recognized the Rock’s potential value as a fortress and constructed some minor fortifications there.

The Rock of Gibraltar first entered the annals of military history in 1309. In that year King Fernando IV of Castile directed a landward siege of the peninsula as one small step in the long campaign to take back Spain from the Moors. The defenders lacked strong fortifications and did not put up much of a fight. According to a medieval chronicle, the Castilians “set up two siege engines and with them attacked it fiercely all the way round, till the Moors could stand it no longer and were forced to parley with the King.” Upon taking possession of the Rock, Fernando recognized that “there was no better look-out post in all his lands,” and ordered construction of a keep, or tower, and a dockyard for his galleys. The military character that Gibraltar thus acquired would last for nearly seven more centuries.

The Moors recaptured Gibraltar in 1333, but the Spaniards did not forget it. The war between Christian and Muslim raged fiercely from year to year, with the now fortified peninsula becoming a bone of contention. The Moors therefore constructed a castle complex, including a tower and redoubt that remain intact to this day. These fortifications helped them fend off multiple Spanish attempts to retake Gibraltar over the following decades. Properly defended, the Rock looked more and more like one of the world’s premier natural fortresses. Not until 1462—thanks to the departure of most of the Muslim defenders to pay homage to a distant king—did Gibraltar pass back into Spanish hands.

As King Henry IV of Castile took possession of Gibraltar, he granted the settlement a charter that took formal recognition of its strategic value by both land and sea. Preoccupied with the continuing war with the remnant of the Moorish emirate in Granada, Henry declared that Gibraltar “stands guard over the Strait to prevent the passage to the King and Kingdom of Granada of men, horses, arms, food supplies and other goods.” He encouraged settlers to build up the town and cultivate the surrounding area so that they should be “better disposed to serve me and defend and protect the city and guard the Strait.” Over the coming years the town grew in prosperity, as its docks and status as a free port attracted merchant vessels from far and wide. The final expulsion of the Moors from Spain in 1492 nevertheless left Gibraltar as something of a backwater—a proud Spanish possession but without any obvious military value.

The growth of the Age of Sail changed all that. In the 16th and 17th centuries, with Spain now one of the great powers, Gibraltar became a naval base, its dockyard facilities substantially expanded. The rise of rival European powers England, France, Holland, and Venice, and the Holy Roman Empire—plying trade and warfare across the world’s oceans—gave the peninsula status as a guardian between the Atlantic and Mediterranean. Spanish galleons sailed majestically past Gibraltar on their way to and from the New World, and their protecting warships used the peninsula as a base. In 1590 and 1607 Spanish ships battled English and Dutch vessels just offshore.

By the early 17th century the upstart English had become a particular menace. English warships—and not a few pirates—plagued the waters off southern Spain. Justifiably alarmed, the Spanish vastly expanded Gibraltar’s fortifications against seaward invasion, building among other things a chain of 44 watchtowers along the coast. The English also noticed the Rock’s growing strategic importance. In 1625 an English naval expedition seriously considered attacking the place but was scared off by the now formidable Spanish defenses. As England’s naval power grew over the following decades, however, it craved Gibraltar more and more as a potential link in the chain that would establish its rule of the seas.

The War of Spanish Succession (1701–1713) provided the English with the opportunity they sought. By the beginning of the 18th century, Spain was awash in New World wealth but in wholesale decline militarily and politically. After the death in 1700 of King Charles II, a Habsburg, the Spanish throne suddenly had a claimant from the House of Bourbon. Since this royal house also reigned in France, England joined with the Dutch and the Habsburg Holy Roman Empire in a war to wrest Spain from Bourbon control and place a Habsburg monarch back on the throne. It was under this pretext—ostensibly to win Gibraltar back for a Habsburg king of Spain—that an English fleet under Admiral Sir George Rooke joined in an allied attack on the Rock in 1704.

In 1702 Rooke had led an expedition to Cádiz that failed disastrously when the soldiers he put ashore discovered the local wine supply and got riotously drunk. Two years later, he had better troops at his disposal—1,800 English and Dutch marines under the command of Prince George of Hesse-Darmstadt. His plan was to place them ashore to seal off the peninsula by land, and then “Bombard & Canonade the Place from our ships, and endeavour by that means to reduce it to the King of Spaines Obedience.” The troops labored ashore in brutal heat on August 1, 1704, and summoned the town and fortress to surrender. The tiny garrison of fewer than 100 veteran soldiers refused. Rooke then commenced his bombardment, fiercely pummeling defenders who manned fortifications that had not been improved since the 1620s.

Sensing an opportunity to storm the defenses, English captain Edward Whitaker ordered 200 sailors ashore to scale the seaward wall. They landed, clambered over the wall, and disappeared. Moments later a huge explosion rocked the fortress, throwing the bodies of dozens of the sailors sky high. At first it seemed that the garrison had blown up the fort’s powder magazine, but it later transpired that the seamen had rushed with “heedless courage” into the magazine “with lighted torches in their hands.” The remnants fled. Whitaker then arrived with reinforcements and attacked the fortress. In the frenzy of battle his men opened fire on a crowd of women and children who had taken shelter in a shrine, killing many of them. British marines then looted the shrine. The garrison surrendered to ensure the safety of their remaining civilians, but though the well born were spared, the poor were not, as English and Dutch sailors sacked the town.

An attempt by the Spanish and the French to retake Gibraltar later that year proved the absolute necessity of coordinated land-naval action for a successful attack. The English navy fended off the few French ships that appeared offshore, but 500 Spanish infantry bravely attacked on November 11 by scaling the Rock’s eastern face. Atop the Rock the English and Spanish Habsburg forces delivered a powerful counterattack that crushed them and sent some Spaniards plummeting over the cliffs of the northern face. Another attempt in January 1705 by 4,000 French and Spanish troops likewise failed. So long as the English controlled the seas, the Rock would remain a tough nut to crack. Later that year the Habsburg “king,” styling himself Charles III, came ashore to celebrate the conquest of Gibraltar on the only part of Spain that he could claim for his own.

Although England had captured Gibraltar, by the terms of its alliance with the Holy Roman Empire, the Rock was supposed to revert to Charles III. A series of coincidences dictated otherwise. In 1711, after two Holy Roman Emperors died, Charles III succeeded them as emperor. The idea of a union of Spain and the Holy Roman Empire under one monarch did not please the British, who thereupon abandoned the alliance. Even so the French were exhausted and sought peace. When that came in 1714, with the end of fighting in the War of Spanish Succession, the Bourbons were in control of Spain—but on condition that the thrones of France and Spain could not be united. As a part of the treaty, the British retained control of the island of Minorca, which they had also captured, and Gibraltar. The seal was set on the next three centuries of the peninsula’s history.

The Spanish refused to accept that they had lost Gibraltar because of a petty dynastic squabble. Their bitterness was further inflamed by British restrictions on the religious freedom of Catholics in the newly conquered territory. It was only a matter of time before the two countries would again come to blows and make Gibraltar a battleground. Fighting broke out in 1727, when the Spaniards mounted another unsuccessful assault by land. Another peace treaty in 1729—after the British had expelled all the peninsula’s Spanish civilian inhabitants—did nothing to ease tensions.

Major William Green, an engineer who was posted to Gibraltar in 1761, knew that the Spanish would try to reconquer the Rock. A veteran of the French and Indian War in North America, Green was highly proficient in gunnery and siegecraft. What he saw at Gibraltar worried him. While the landward defenses were strong, those to sea were not. British command of the Mediterranean around Gibraltar was robust but could never be guaranteed.

Gibraltar’s governor backed up Green, remarking, “Though it has often been said that Gibraltar is impregnable, which no place is according to my notions, it was always understood ‘while you command the sea.’” In 1769 Green’s plans for an overhaul of the Rock’s fortifications were approved in London. He set to work with a special company of “soldier artificers,” and under his expert eye the artificers completely transformed Gibraltar, constructing massive fortifications that included the huge King’s Bastion.

The improvements came in the nick of time. In 1775 the American Revolutionary War began, and a few years later the French and Spanish intervened against Great Britain. For Spain, North America meant little compared to the Rock, which they eagerly wanted back. Their determination culminated in the so-called Great Siege. From 1779 to 1783 the Spanish did their best to blockade the peninsula by both land and sea and made multiple attempts to capture it. The defenders, vigorously led by General George Augustus Eliott—assisted ably by Green—successfully repulsed every attack. Laid low at times by short rations and disease, they never came close to surrender. After a final massive bombardment by Spanish and French forces from land and sea failed spectacularly in September 1782, the truth became obvious: Thanks to Green’s fortifications, the Rock had indeed become impregnable.

After the Great Siege, Gibraltar became a renowned symbol of British imperial power. During the Napoleonic Wars it served as an important naval base. In 1805 Gibraltar received the body of Admiral Horatio Nelson—preserved in a cask of brandy—after his death in the nearby Battle of Trafalgar. During the Peninsular War (1808–1814) the French groped toward but never came close to seizing the Rock. British support of the Spanish rising against Napoleon contributed to a fleeting period of goodwill between the two nations, and for a short time after Napoleon’s final defeat in 1815 it seemed as if the Spanish had almost—but not quite—come to terms with British control of Gibraltar. During the 19th century the town below the Rock grew into a thriving community alongside the military garrison. The British government nevertheless continued to improve the Rock’s already formidable defenses, renovating fortifications and installing the latest designs in heavy artillery.

The outbreak of the First World War brought Gibraltar straight back into the headlines. In the first two days after Britain’s declaration of war on Germany in August 1914, torpedo boats darted out of Gibraltar and captured four German ships, proudly escorting their prizes back into the Rock’s shadow. German surface ships soon disappeared from the seas, however, and Gibraltar settled back into its daily routines. The appearance of German U-boats in the Mediterranean in 1915 found the British unprepared. The kaiser’s submarines passed through the straits and below the Rock with impunity, going on to raid Allied shipping. The British garrison looked on in frustration but could do nothing to stop them. In 1917 and 1918 Gibraltar served as an assembly point for ocean convoys, but that was about the extent of its contribution to the war effort.

World War II brought Gibraltar back into the strategic picture. Although Spanish dictator Francisco Franco adopted a deliberately nebulous nonbelligerent posture, his pro-Axis leanings were well known, and there was always the possibility he would throw in his lot with Hitler and Mussolini. Nor did he make any secret of his resentment of British control of the Rock. As a precaution, most of the peninsula’s civilians were evacuated to Great Britain. If Hitler had succeeded in bringing Franco into the Axis or if Germany had invaded Spain, Gibraltar would surely have been in deep trouble. As Winston Churchill wrote, “The Rock might once again stand a long siege, but it would only be a rock. Spain held the key to all British enterprises in the Mediterranean.” It was a good thing for the British that Spain stayed out of the war.

Gibraltar did come under attack from German and Italian aircraft, which sometimes bombed the peninsula but caused little damage. The greatest immediate danger came from Italian frogmen under the command of Prince Valerio Borghese, an aristocrat and enthusiastic Fascist. He attempted multiple methods for damaging shipping in Gibraltar’s harbor from 1940 to 1943. One involved frogmen from the Italian submarine Sciré. The frogmen guided manned torpedoes toward British merchant ships and attached explosive charges to their hulls before swimming ashore, where Italian agents picked them up and smuggled them out of Spain. More often than not, these attempts failed or caused only minor damage, but in 1942 Borghese hit on the ruse of basing his frogmen in the hulk of an old Italian merchant ship in nearby Algeciras harbor. Over the course of about two years Italian frogmen managed to attack and sink or damage a total of 14 merchant ships before Italy signed an armistice with the Allies in September 1943.

Meanwhile, the British garrison at Gibraltar busily expanded its tiny airfield. U-boat commanders could no longer thumb their noses when they passed the Rock, as they had in the previous war. Although the British suffered some serious shipping losses early in the war from submarines operating nearby—including the aircraft carrier HMS Ark Royal, sunk by U-81 30 miles from Gibraltar on November 13, 1941—fighters and seaplanes based at the Rock soon made passage of the straits a risky proposition for U-boats. Convoys assembled under Gibraltar’s protection to carry vital supplies to British forces in North Africa. And the November 8, 1942, Allied invasion of Vichy French North Africa—Operation Torch—was headquartered in Gibraltar.

Although Gibraltar lost its status as an important military and naval base after 1945, it grew in prominence as one of Western Europe’s few remaining political flashpoints. While the British disassembled their worldwide empire, they very pointedly held on to the Rock, much to the chagrin of Franco—who ruled until 1975—and his successors. Spanish anger failed to stir the Gibraltarians, who by now firmly identified themselves with Great Britain. Although military confrontation is unlikely, tension over Gibraltar has evolved into an on-again, off-again mini–Cold War, with the Spanish occasionally imposing severe restrictions on access and trade. In the 21st century there seems little prospect that this state of affairs will change. Rather, tiny Gibraltar is poised to loom large in Europe for many years to come.


Edward G. Lengel, director of the University of Virginia’s Papers of George Washington project, writes about many periods of history. He is now completing a World War I prequel volume on American military engagements in 1918.

Originally published in the July 2014 issue of Military History Quarterly. To subscribe, click here.