Originally Posted By: stracci
I wasn't sure how Vito knew it was Barzini (still might not be totally sure)


Most here would agree that it was Barzini's dominance at the "Big Meeting". He took the leadership role in summarizing the agreement on the narcotics issue. Vito saw that as Barizini muscling in on the action and thus muscling the Corleone's out.

Whoever exalts himself will be humbled, whoever humbles himself will be exalted - Matthew 23:12