The novel states that, about a decade before the Sollozzo affair, a group of "mad dog Irish killers, with sheer Emerald Isle elan," burst through Vito's protection, and shot and nearly killed him before they were cut down, leading to Sonny's rise.
(Its a good book, you should read it.)
Yes Frank, Ice is correct. And Let me add, as I explained to you in an earlier PM that I sent you, that it was Luca Brazi who singlehandedly took out the Irish mob who had shot Vito, in the throat, which eventually caused him to talk in that rough and course voice that he talked in. That Is exactly why I feel that Sollozzo, Tattaglia and Barzini knew that in order for them to increase their odds of defeating the Corleones, Luca Brazi, the Don's greatest ally, had to be taken out first. No matter if they believed Luca was switching sides or not, it was a chance that they could not take because with Luca out of the picture, it would give them a better chance at defeating the Corleones.
Take out Luca and try to take out Vito, then the hotheaded Sonny would either deal with them or act out of haste and lose his own life, and the Corleone's would be done. It was a very good plan.
But little did Barzini, Sollozzo and Tattaglia know that the college boy son, who wanted nothing to do with the family business, would eventually be the cause their demise.
What a plot!
Don Cardi