TB, your interpretation is reasonable. However, I tend to side with Pete about Barzini's breaking the peace. As Pete intimates, the peace subsumed a whole lot of underworld activity. That interpretation is supported by, in the novel, the Dons' agreement that certain cities were to be open to any families operations. If any Don wanted to be technical about it, I suppose they coul dmake an argument that encroachments on other families territory wasn't an explicit part of the peace.