The fifth column

The nationalist advance on Madrid began at the end of the first week of October (1936). General Mola claimed 'that he had four columns attacking the capital and a "fifth column" of sympathizers within the city ready to revolt.'  (Beevor, 2006, p166, 168)

At around the same time, there was the 'Battle Of Cable Street' in London. Bill Fishman recalls:

It seemed like an act of solidarity because, on the same day, the Republicans in Spain were also preparing to defend Madrid against General Franco's fascists.
(DAY I FOUGHT THE FASCISTS, Daily Mirror, 23 September 2006)

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