[fifilura]

A fifth column is a group of embedded traitors.

I am not sure the word is suitably used here.

Franco (loosely). "We'll be marching towards Madrid in four columns. The fifth column is already in the city".

[ebb_earl_co]

As in Francisco Franco? Thank you for the definition and some bonus etymology!

[fifilura]

Yep same guy, during spanish civil war in the 1930s