How did Vito Corleone know it was Barzini all along?

In the Godfather 1, we are introduced to the behind the scenes of the dark criminal empire run by the notorious don Vito Corleone. We all watched the intriguing series of events unfold, and the story was brilliantly made by the legendary Francis Ford Coppola, based on the iconic work of Mario Puzo the creator of the original novel. But there is something that until today has us wondering, a question that wasn’t clearly answered and still captivates many debates. That question is, how did Don Vito instinctively know that the individual behind all these treacherous events was not the obvious Philip Tattaglia, rather the more cunning, Don Emilio Barzini?