Tom was first and foremost a lawyer, and so his thought process was always leaning more toward settling things without killing people and making a deal. Vito's quote in the novel, cited above, but not re made in the film is off base. A lot of what went wrong was Sonny's fault. Clemenza screwed up security with Paulie, and Vito got shot because Barzini and the other families wanted into the drug business, and they knew that Vito and Sonny had different views on it. Both Sonny and Michael wewre always quick to blame Tom for his non-Sicilian way of thinking, but also quick to rely on him. Bottom line, Sonny was a terrible Don, and Michael was...well Michael. Tom was not a wartime consigliere, but otherwise a good consigliere and a great lawyer.

I always wonder where he went to law school. Since he lived with the Corleones, I am guessing Fordham, or NYU.