A fifth column is a group of people who clandestinely undermines from within a larger group to which it is expected to be loyal, such as a nation. The term originated with a 1936 radio address by Emilio Mola, a Nationalist general during the 1936-39 Spanish Civil War. As four of his army columns moved on Madrid, the general referred to his militant supporters within the capital as his "fifth column," intent on undermining the Republican government from within.
The term is also used in reference to a population who are assumed to have loyalties to countries other than the one in which they reside, or who support some other nation in war efforts against the country they live in.
During World War II, German minority organisations in Poland and Czechoslovakia formed Selbstschutz, which actively helped the Third Reich, against those countries have engaged in atrocities.
The Japanese American internment in the United States was justified on the basis that those of Japanese ancestry living on the west coast would act as a fifth column. Irish Catholics resident in the UK have been sometimes viewed in this way due to "The Troubles" of the late 20th century (see also Guildford Four, Birmingham Six).
Today it has sometimes a pejorative connotation, whereas partisan can be considered good or bad, depending on one's perspective. Resistance movements are looked upon more favourably than fifth columnists, but it can be argued that that there is an overlap between the two.
Today some people in a number of Western countries see radical Islamists - or even Muslims in general - as being a fifth column of a global Islamist movement, with its notion of a transnational Ummah.
