Army chiefs were urged to fight aliens with nukes, according to a secret document.
It sets out how the US Army would need to prepare for war with Martians.
But they would have to develop new weapons, vehicles and moon bases to take on hostile ETs.
The opening page states: "The United States may be called upon to wage extra-terrestrial warfare within the next two to three decades.
"This paper explores the implications of this requirement for the US Army and proposes a program of studies that will enable the Army to meet this requirement."
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