One of the command posts of the P Line, created to defend Spain during World War II

Although during World War II Spain was a neutral country, there were plans to invade it from both Germany and the Allies.

The remains of a Czechoslovakian tank in the French-Spanish border bunkers
The shelter and bunkers of the Spanish Civil War in Calella de Palafrugell, Gerona

Germany planned the so-called Operation Felix, which would have aimed to conquer Gibraltar and a possible invasion of Portugal, which has traditionally been an ally of the United Kingdom. The experience of the Napoleonic invasion of Spain at the end of 1807, with the excuse of taking Portugal, indicated the danger that this operation contained. On the other hand, the Allies prepared the so-called Operation Backbone to invade Spain in case the Franco regime decided to enter the war on the side of Germany. The fear of an Allied intervention in Spain increased in 1944, after the liberation of France, and especially at the end of that year, when the guerrilla operations of the maquis, mostly Spanish communists, began in the Pyrenees.

Because of this, already in 1939 the Franco regime began the construction of the so-called Line P in the Pyrenees, a network of fortifications that would have been intended to stop an invasion of Spain from France. 10,000 forts were planned, of which about 4,000 were built, ending the construction works in 1948. You can see here a map of the forts that are preserved today.

This Friday, the always excellent YouTube channel Aventuras Entresieras (I recommend you subscribe if you like interests the world of exploration) published an interesting video in which he tours a command post on Line P in the Alto Ampurdán region, in the province of Gerona. In the video we can also see the Monte Rojo Castle, in the town of Darnius (Gerona), and a Line P bunker next to it (the video is in Spanish, you can activate the automatic English subtitles in the bottom bar of the player):

You can see some screenshots from the video below. We start with the entrance to the P Line command bunker, with excellent construction and well preserved. As you can see in the video, inside there are long stairs to access the different galleries.

In this same area there is a plaque in French that commemorates General Jacques Dugommier (1738-1794), who fell in Darnius during the Roussillon War or War of the Pyrenees (1793-1795), during which The young French Republic attempted to annex the Spanish region of Catalonia.

The ruins of the Monte Rojo Castle (or Mont-Roig, in Catalan). It is a fortress of medieval origin, possibly built in the 11th century and which was destroyed during the aforementioned Roussillon War, during the Battle of Roure, in which the aforementioned French general died.

The P Line bunker located next to the Monte Rojo Castle. It would be an observation post. The bunker is less than 10 km south of the French border.