15-Inch Vickers Battery at Fortalesa Isabel II


Last summer I was lucky enough to visit the vast Fortalesa Isabel II which defended the port of Mahon, in Menorca. One of the fort’s most impressive sights is its huge 15 inch gun battery.

The Spanish island of Menorca, in the Balearic Islands, has a long and storied military history. The strategically important harbour of Mahon was historically the envy of the British, Spanish and French and was the reason for Fortalesa Isabel II’s construction. The for was the last major fortification built on the island, with the Spanish military beginning construction in 1850. A second phase of major improvements was made during 1853-1864. Work to improve and modernise the fort continued into the 20th century.

Fortalesa Isabel II main gate (Matthew Moss)
The ornate main gate of the fort, defended by a counterguard and rifle slits either side of the gate (Matthew Moss)

The Fortress is built on a beautiful rocky headland of La Mola at the mouth of the harbour and covers about a square kilometre. Construction was a massive undertaking and took over twenty years to complete, costing over nine million pesetas. The fortifications are some of the Mediterranean’s most impressive of the period.

The fort is a maze of tunnels, galleries, casements and buildings surrounded by a deep, dry moat. The fort’s first line of defence consisted of a moat 9 metres (30 feet) deep covered by rifle loop holes for infantrymen and embrasures for artillery. Interlocking fields of fire defend the landward approach to the fort’s main entrance, the Queen’s Gate.

Map of the La Mola peninsular and fort
Map showing the layout of the fort during the 19th century before the 15 inch guns were added (source)

Designed to dominate the entrance to the harbour the fortress was intended to hold 160 artillery pieces of various sizes, including Krupp guns and howitzers, many of these protected by strong stone casements. The fort’s armaments evolved overtime from muzzle-loaders to faster firing breech-loaders.

The Spanish continued to upgrade the fort’s guns over the decades mounting rifled guns and howitzers of various calibres ranging from 15cm to 30.5cm. In addition to the fort’s guns the defences also included mines in the harbour mouth and later a battery of shore launched torpedoes.

By the early 20th century the fort’s guns were increasingly obsolete against the backdrop of the naval revolution that saw Dreadnoughts come to dominate maritime warfare. With advances in naval architecture, armour and guns the Spanish government decided to purchase a number of massive 15 inch naval guns that could fire a 1,895 lb (860kg) shell up to 22 miles.

One of La Mola's 15 inch guns in position
One of the fort’s two 15 inch Vickers guns in position on Cape Espero (Matthew Moss)

Spain purchased 18 of these massive guns made by the British Vickers company, they had originally been designed for the cancelled Brazilian battleship Riachuelo. In Spanish service the guns were officially designated the Costa de 38.1cm Modelo 1926. During the 1930s the new coastal guns were installed on both the Spanish mainland and Menorca. Two guns placed in the Castillitos Battery, defending Cartagena, opened fire on a Spanish Nationalist fleet, during the dying days of the Spanish Civil War. While Menorca’s guns never fired a shot in anger, they acted as a deterrent.

The first guns reached Mahon in 1932, with a second arriving in 1936, these were mounted on the cliffs of Cape Espero on the La Mola peninsular. The guns were so huge they had to be transported to the fort on a specially built railway pulled by hand and traction engine. These formidable new guns brought Fortalesa Isabel II’s armament up to date, enabling it to protect Mahon from any modern warship.

15 inch gun being dragged by a traction engine through mahon
One of the massive 15 inch guns being pulled along its special track by a traction engine through the streets of Mahon (source)

The 15 inch (or 381mm) Vickers battery at the fort was positioned 70m above sea level and commanded the entrance to the harbour. Six guns were eventually sent to Menorca with two  placed on La Mola, two more installed in a battery at Favaritx (the remains of which can be seen here) in the north of the island and a pair at a battery near Llucalari in the south of the island.

While the guns at Favaritx were later removed, the guns at Llucalari remain. The fact that six of these massive and expensive naval guns were placed on Menorca shows its strategic value during the period.

Satellite photo of the 15 inch battery at Llucalari
Satellite photo showing Menorca’s other 15 inch battery at Llucalari (google maps)

The guns were mounted in barbettes which allowed the guns to traverse up to 300 degrees. The gun housing of the turret was armoured but while it would not protect the crew from a direct hit, it would protect against shrapnel. Below the guns were magazine stores for both cordite charge bags and projectiles, the machinery needed to rotate and move the gun and the motors to power it. Inside the turret were controls to open and close the breech, lift and lower the loading tray and aim the gun. The guns had a potential maximum range of 35km or 22 miles, however, the guns at La Mola lacked the necessary range-finding equipment to achieve this range.

Inside the 15 inch gun turret
A contemporary photograph showing the interior of the gun turret. A shell is sat on the loading try ready to be pushed into the breech. (source)

The ancillary buildings for the battery on La Mola are built just behind the two gun emplacements with offices, stores and barracks built in an old quarry. As well as the two main guns the battery was supported by four faster firing 6 inch Vickers guns.

15 inch Vickers gun firing in the 1980s
One of Menorca’s 15 inch guns firing c.1980s (source)

With the eruption of the Spanish Civil War in 1936, Menorca was initially held by the Republicans. But in 1939, the island fell to General Franco’s Nationalists and the fort’s military prison was used to house a number of prominent Republican prisoners. Throughout the Cold War the fort continued to be used by the Spanish Army as a training centre but the rise of air power, the invention of the cruise missile and nuclear weapons rendered the fort and its guns increasingly obsolete.

The last of Spain’s 15 inch guns were finally decommissioned in the mid-2000s, after nearly 80 years in service. Fortalesa Isabel II and her two massive guns never saw action, and today the site is maintained as an impressive museum which is well worth a visit.

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Length: 18m or 59 feet
Weight: 86.9 tons
Action: breech-loading
Calibre: 15 inch or 381mm
Elevation -5 / +40 degrees
Traverse: 300 degrees
Rate of fire: 2 rounds per minute


The Fortress of Isabel II on La Mola in Mahon Harbour (19th 7 20th Century), F. Fornals (2007)

The Conquests and Reconquests of Menorca, M. Mata (1984)

Guns of Cartagena, espele.net, (source)

‘Yo hice la Mili en La Mola de Menorca’, Facebook group with excellent contemporary photos (source)


Please do not reproduce photographs taken by Matthew Moss without permission or credit. ©The Armourer’s Bench 2018.