[Recruits] ought to perform physical exercises, mainly of two types: an agile gymnastic with training for war of a commando type, which demands agility in attack and withdrawal; and hikes that are hard and exhausting that will serve to toughen the recruit for this kind of existence. Above all, they should live in the open air. They should suffer all the inclemencies of the weather in close contact with nature, as the guerrilla band does.

• Comrade Che, Guerilla Warfare (1961)