TB, you're right about what precipitated the war. But for some reason I've never felt comfortable with Sonny's outburst being the motivation for Sollozzo's attempted murder of Vito (despite that that's what Puzo/FFC want us to believe). Had the murder succeeded, there are several ducks that had to be in a row for that murder to have the desired outcome. For one, Sollozzo would have to count on Sonny's viewing the murder as just business and his not going after Sollozzo with blind fury. One other duck is that Sonny could assume effective control of the Corleone family and provide the drug operation with the political and legal cover that Sollozzo wanted. The last one is that when Sollozzo entered the meeting he didn't know that Sonny would be hot for his drug deal. So, either Sollozzo entered the meeting prepared to accept Vito's possible No or that he would murder Vito anyway as a result of that No.