Oli, I looked in the novel just now. There was no "it was Barzini all along" anywhere. In his narrative describing the Dons at the Commission meeting, Puzo writes: "The closest ally to the Tattaglia Family was Don Emilio Barzini." A page later, describing Tattaglia, Puzo writes: "In a curious way his almost victorious war against the Corleone Family had not won him [Tatt] the respect it deserved. They [the Dons] knew his strength had come first from Sollozzo and then from the Barzini Family."