A very basic, fundamental question that surely must have been raised on this forum more than once before, though I can find no evidence of it: During the latter part of GF1, after Michael had assumed full control of the Corleone family and begun the family's transition to Nevada, Vito warns Michael of an impending assassination attempt against him. Not only can Vito foresee that the attempt is coming, he is also able to furnish Michael with important details, i.e. that the attempt will be initiated by Barzini, that it will occur at a meeting, set up by someone close to the family, whom Michael absolutely trusts, thereby guaranteeing his safety.

Simply, how did Vito know all this? That Barzini would be the culprit is somewhat logical, but for the fact that the Corleones would soon be leaving New York anyway - which Barzini would already know about from Moe Greene, who "talks to Barzini" - thereby no longer presenting any challenge to Barzini's interests. So why murder Michael, when the Corleones are already "getting chased out of New York"?

Even more to the point, how could Vito have known the manner in which the assassination attempt would be carried out, with such specificity? I can't even speculate about the answer(s) to that, other than to guess that it's rooted in some kind of Mafia custom or "standard operating procedure" that goes back to the Mustache Pete era.

Thoughts? Ideas?