I still see a clear difference (as posted above): a guerrilla is always a fighter while an insurgent is a more overall term which can be a fighter or not (he may be a pure politician, a bomb-maker, a journalist who writes articles on the Internet, a webmaster, a photographer/cameraman, a computer expert, ...)
So in my opinion you're talking about a guerrilla and an insurgent fighter.
He obviously didn't fail in Cuba.
He failed later on in Africa and South America because he focussed on Guerrilla TTPs (in his book he also mainly writes about pure tactical stuff) while he failed to notice the absence of a political situation that favours an insurgency.
BRUZ
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