SS Cantabria was a Spanish-owned cargo steamship that was built in 1919 in Canada and sunk in 1938 in a naval action in the Spanish Civil War in the North Sea.

[8] In 1937 the Departamento de Navegación of Santander requisitioned her for the Republican government and renamed her Cantabria.

She was in passage in ballast from the River Thames to Immingham, whence she was to sail for Leningrad under Captain Manuel Argüelles.

She was converted from the merchant ship Ciudad de Valencia,[10] and took part in the blockade of the Bay of Biscay in 1937.

The Nationalists had renamed her to deceive the Spanish Republican Navy about the real number of commerce raiders at sea.

She had been launched on 18 October 1930 at the shipyard Unión Naval de Levante [es] as Infante D. Gonzalo, owned by the Compañía Transmediterránea.

Cantabria's wireless telegraph operator had been sending signals that she was "being shelled by unknown vessel".

[14] It was now nearly dark and at 5pm the Cromer Lifeboat H F Bailey with coxswain Henry Blogg at the helm was launched to rescue Cantabria's crew and passengers.

This House of Lords judged this to be unlawful interference in British shipping, as Nadir obstructed the legal duty of rescuing seamen.

Argüelles signalled the lifeboat with a torch, and it pulled along the starboard side of Cantabria, which was heavily listing.

Argüelles, his family and the steward were taken to the Red Lion Hotel, and Pattersonian took the other 11 rescued crewmen to Great Yarmouth.

The BBC reported an account of the incident, along with a warning to shipping, giving the sunken Cantabria's position.

British newspapers carried the story as headline news, but many of the crew at Yarmouth refused to be photographed, fearing Nationalist reprisals.

[21] For some time, the Danish police had been interested in the Copenhagen correspondents for a German newspaper, one of whom was Horst von Pflugk-Harttung.

[22] Danish police arrested Harttung and eight other Germans living in Denmark, along with three Danes, and charged them with operating as spies in Copenhagen.

Danish police proved that the accused had all been trained at Gestapo spy schools and had operated secret broadcasting stations, as well as engaging in nautical and hydrographical research.

The spy ring used the shadowing and sinking of Cantabria to demonstrate the complicated subversion mechanism that the Gestapo was developing.

[12] Horst von Pflugk-Harttung was a German spy, who along with his brother Heinz, had previously been charged in Berlin for the assassination of the Socialist leaders, Karl Liebknecht and Rosa Luxemburg.

After Horst von Pflugk-Harttung's trial in Denmark,[23] he was sentenced to only a year and a half in prison, and was released after a few months after German government pressure.