Breaking the Iron Belt, Spain, June 1937 (background history)

Breaking the Iron Belt

Bilbao, June 1937 

The Francoist conquest of Guipúzcoa in October 1936, left the northern part of Republican Spain isolated from France and in a precarious position. From then on, it was supplied by sea, but the bulk of the Francoist fleet was concentrated in the Cantabrian Sea, which made it dangerous for Republican merchant shipping.

On March 31, 1937, General Emilio Mola sent his armies to take the northern front, starting with Vizcaya. They had more men and more equipment than the Republicans, who were also divided into three autonomous political units: the Basque Country, Asturias, and Santander, each with its own militias and little cooperation among them. Moreover, these forces had not evolved at the same pace as the regular army in the rest of the Republican zone. Even so, a campaign Mola expected to be over in a few weeks lasted seven months. There were two main reasons for this: the mountainous terrain and staunch Republican resistance.

The forces defending Vizcaya were made up primarily of 27 Basque nationalist battalions, 8 Socialist ones, and 11 assorted others. The Republic did everything possible to send military equipment north, including planes that flew over enemy territory, but the attackers, who included Italians and Carlist militias, enjoyed a clear superiority in arms and materiel. The unexpectedly stiff Basque resistance, assisted by Republican offensives in Segovia and Huesca, led the Francoists to take extreme measures to terrorize the population. The most famous was the bombing of Guernica in which 300 people were killed.  

The Iron Belt "Cinturón de Hierro", or Bilbao Defensive Belt, was a horseshoe-shaped fortified line built between October 1936 and June 1937 to protect Bilbao. Extending over a perimeter of eighty kilometres, the project was made up of multiple, often incomplete, lines of trenches, bunkers, and machine gun nests designed by Alberto Montaud Noguerol, a professor of fortifications. It was a regional adaptation of the static warfare model, similar to the Maginot Line; drawing on the city’s historical resilience demonstrated during multiple nineteenth-century Carlist sieges. However, despite the extensive coverage, it was an antiquated defence concept similar to WW1 fortifications, which made it vulnerable to modern warfare weapons of the time, such as aircraft and artillery. Additionally, the fortifications were designed to hold 70,000 troops but were eventually only held by 30,000, less than half conceived to defend it.

Also, from its inception in October 1936, the project faced significant logistical and political obstacles, including shortages of materials, transport, and labour. Internal security was also compromised: among its engineers, Pablo Murga was arrested and executed for espionage in November 1936, while Alejandro Goicoechea defected in February 1937.

Goicoechea provided the Francoists with crucial details, including the fortifications’ plans and status, revealing a poorly fortified sector centered on Mount Gaztelumendi and the small town of Larrabetzu, which later became the focus of the offensive.

Between 11 and 12 June 1937, a major assault was launched on the Belt, beginning with a coordinated bombardment involving 144 artillery pieces and aircraft from the German Condor Legion and Italian Legionary Air Force. This was followed by a successful infantry advance through the weakly fortified Gaztelumendi sector, triggering a general Republican retreat towards Bilbao.

The city fell on June 19. The decision of the Basque government not to destroy the region’s important heavy industry meant that the rebels inherited it intact.

My Plan

Using this background history I`m going to try and run three linked games set during the period 11/12 June 1937. As always I`m going to take some liberties with forces on both sides as these games will be just tabletop representations and NOT reenactments of the actual events.