These Visitor members are known as the Fifth Column. In V the Fifth Column are a group composed largely of officers, and intellectuals that oppose their leaders plans for the Earth. The fifth column supplies weapons, uniforms, escape methods and tactical information for human resistance members that proves invaluable to the efforts to fight the Visitor war machine.

For their efforts, the fifth column are given an antidote to the red dust toxin which allows them to live while much of their brethren are killed by the red dust bacterial agent. Notable fifth columnists throughout the V saga are Martin, Phillip, Oliver, and Barbara.

The term fifth column refers to any subversive agents who attempt to undermine a nation's solidarity according to the Encyclopedia Britantica. The source of the phrase fifth column probably comes from the Spanish Civil War. Nationalist general Emilo Moloa referred to members of his forces hiding within Spain's capital city as a Fifth Column waiting to rise up and strike the capital from within.

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