Strait of Gibraltar

Gateway Between Two Worlds

7 min read 1,467 words mediterranean maritime-strategy europe africa naval-power 0% read

The ancient Greeks called them the Pillars of Hercules—the twin promontories marking the western boundary of the known world. On the European side, the Rock of Gibraltar rises 426 meters above sea level, a sheer limestone monolith visible from 100 kilometers away. On the African side, Jebel Musa in Morocco stands as its companion. Between them flows the Strait of Gibraltar: just 14.3 kilometers wide at its narrowest point, 58 kilometers long, and approximately 300 meters deep at its shallowest—a geographic bottleneck through which every vessel entering or leaving the Mediterranean Sea must pass.

This constriction has made Gibraltar one of the most strategically significant locations on Earth for over three thousand years. The Phoenicians passed through it to establish Carthage. The Romans controlled it to make the Mediterranean their mare nostrum—“our sea.” The Moors crossed it in 711 to conquer Iberia. The Spanish and Portuguese contested it during the Reconquista. Britain seized the Rock in 1704 and has held it ever since, using it as the cornerstone of a maritime strategy that dominated global politics for three centuries. Today, approximately 100,000 vessels transit the strait annually, carrying roughly 20% of global seaborne trade—including oil tankers from the Persian Gulf that pass through the Suez Canal and then through Gibraltar en route to Atlantic markets. The strait’s strategic importance has not diminished with time; it has grown.

Geography

The Chokepoint

The Strait of Gibraltar connects the Atlantic Ocean to the west with the Mediterranean Sea to the east. The Mediterranean, despite being partially enclosed, provides access to 22 countries across three continents, hosts major naval bases, and serves as the primary maritime route between Europe and the Middle East via the Suez Canal.

The strait’s physical characteristics make it both navigable and controllable:

  • Width: 14.3 kilometers at the narrowest point (between Point Marroquí in Spain and Point Cires in Morocco), expanding to approximately 44 kilometers at its western entrance
  • Depth: Approximately 300 meters at the shallowest sill, reaching 900 meters in the central channel—deep enough for any vessel, including nuclear submarines
  • Currents: A powerful two-layer current system: Atlantic water flows east along the surface (driven by evaporation in the Mediterranean, which makes it saltier and denser), while denser Mediterranean water flows west along the bottom. These currents, combined with tidal forces, create challenging navigation conditions
  • Traffic: Approximately 300 vessels transit daily, making it one of the world’s busiest waterways. This includes container ships, oil tankers, bulk carriers, naval vessels, fishing boats, and—increasingly—migrant boats

The Rock

The Rock of Gibraltar dominates the northern shore of the strait. This 6.7-square-kilometer peninsula—connected to Spain by a narrow isthmus—has been a British Overseas Territory since the Treaty of Utrecht (1713). Its strategic value lies in its position: any vessel transiting the strait passes within range of guns, missiles, or sensors stationed on the Rock. During both world wars, Gibraltar served as a critical naval base, controlling access to the Mediterranean and providing a staging point for Allied operations.

The Rock’s interior is honeycombed with tunnels—over 50 kilometers of them—carved by British military engineers over three centuries. During World War II, the tunnels housed a complete military headquarters, hospital, ammunition magazines, and barracks for 16,000 troops. The fortress was considered impregnable; Hitler’s plans to capture it (Operation Felix) were never executed.

Historical Significance

The Ancient World

Control of the strait shaped ancient Mediterranean civilization:

The Phoenicians (c. 1100 BCE) were the first to establish regular transit through the strait, founding trading colonies including Cádiz (Gadir) on the Atlantic coast of Spain—one of the oldest continuously inhabited cities in Western Europe. Their passage through the Pillars of Hercules opened the Atlantic to Mediterranean commerce.

Rome’s domination of the Mediterranean—achieved after the defeat of Carthage in the Punic Wars (264-146 BCE)—depended on controlling both shores of the strait. The Mediterranean became mare nostrum, an internal Roman lake whose security required that no hostile power command the narrow entrance.

The Moorish Conquest and Reconquista

In April 711, the Berber general Tariq ibn Ziyad crossed the strait from Morocco with approximately 7,000 warriors, landing at the Rock that would bear his name—Jabal Tariq, “Tariq’s Mountain,” from which “Gibraltar” derives. Within seven years, Muslim forces had conquered most of the Iberian Peninsula, establishing al-Andalus—a civilization that would endure for nearly 800 years and profoundly shape European culture, science, and architecture.

The Reconquista—the Christian reconquest of Iberia—took 781 years (711-1492). Control of the strait was essential: it was both the route through which Muslim reinforcements arrived from North Africa and the passage that Christian kingdoms needed to secure to prevent further invasion.

British Gibraltar

Britain captured Gibraltar in 1704 during the War of the Spanish Succession. A combined Anglo-Dutch force seized the Rock from its Spanish garrison, and the Treaty of Utrecht (1713) ceded it to Britain “in perpetuity.” Spain has contested this cession ever since—a diplomatic dispute that remains unresolved three centuries later.

For Britain, Gibraltar was the cornerstone of a maritime strategy that controlled the world’s key chokepoints. The Royal Navy’s network of bases—Gibraltar, Malta, Suez, Aden, Singapore, Hong Kong—controlled the sea routes of the British Empire. Gibraltar’s position at the entrance to the Mediterranean made it essential: no hostile fleet could enter the Mediterranean without passing under British guns.

During both world wars, Gibraltar played crucial roles:

  • World War I: The base protected Allied shipping in the western Mediterranean and the approaches to the Suez Canal
  • World War II: Gibraltar was the staging point for Operation Torch—the Allied invasion of North Africa (November 1942). General Eisenhower directed the operation from tunnels inside the Rock. The base also protected convoys supplying Malta and supported anti-submarine operations in the Mediterranean and Atlantic

Contemporary Dynamics

NATO’s Southern Flank

Gibraltar remains a key NATO asset. The base hosts British naval and air forces that monitor the strait, track submarines, and project power into the Mediterranean. NATO’s maritime strategy for the southern flank depends on controlling access to the Mediterranean—a mission in which Gibraltar is irreplaceable.

The strait’s significance has grown as security threats in the Mediterranean have multiplied. Russian naval activity in the Mediterranean has increased substantially since 2015, when Russia established its naval task force in the eastern Mediterranean to support operations in Syria. Russian submarines transit the strait regularly, monitored by NATO surveillance assets.

Migration

The strait has become one of the primary routes for irregular migration from Africa to Europe. The 14-kilometer crossing—visible from shore on clear days—attracts migrants willing to risk dangerous currents and overloaded boats. Spanish and Moroccan coast guards intercept thousands of migrants annually, and the human cost is substantial: hundreds drown in the strait each year.

The migration pressure has transformed the strait from a purely military-strategic chokepoint into a political and humanitarian flashpoint. Morocco’s control of migration flows gives it leverage over Spain and the European Union—leverage that Rabat has demonstrated willingness to use.

The Spain-UK Dispute

Spain has never accepted the loss of Gibraltar. The dispute intensified after Brexit, when Gibraltar—which voted 96% to remain in the EU—found itself outside the European single market. Negotiations over Gibraltar’s post-Brexit status, including border arrangements and Spanish proposals for shared sovereignty, remain ongoing.

The territory’s 34,000 residents overwhelmingly oppose any transfer of Sovereignty to Spain—a 2002 referendum rejected shared sovereignty by 98.5%—and Britain has repeatedly committed to respecting the Gibraltarians’ wishes. The dispute, while unlikely to produce military conflict, remains a persistent irritant in British-Spanish relations and a reminder that control of strategic chokepoints generates political contests that can endure for centuries.

Trade Route

The strait’s commercial significance is enormous. Approximately 100,000 vessels transit annually, carrying goods between the Atlantic and Mediterranean markets. The Mediterranean route—through the Suez Canal to the Indian Ocean and beyond—is one of the world’s primary trade arteries. Any closure of the strait would require Atlantic traffic to bypass the Mediterranean entirely, adding thousands of miles and billions of dollars in shipping costs.

Sources & Further Reading

  • Gibraltar: The Greatest Siege in British History by Roy Adkins and Lesley Adkins — A vivid account of the Great Siege (1779-1783), when Spain and France attempted to retake the Rock, and its significance for British imperial strategy.

  • Prisoners of Geography by Tim Marshall — The chapter on Europe explains how chokepoints like Gibraltar have shaped geopolitics and why control of narrow waterways remains strategically decisive.

  • The Mediterranean and the Mediterranean World in the Age of Philip II by Fernand Braudel — The masterwork of Mediterranean historical geography, demonstrating how the sea and its chokepoints shaped civilizations over millennia.

  • Sea Power: The History and Geopolitics of the World’s Oceans by James Stavridis — A former NATO Supreme Allied Commander’s analysis of how maritime chokepoints, including Gibraltar, shape contemporary strategy.